doctorhydrogen

30 lands is really, really lean for a three color deck. I run 37 in mine, and that is in a meta with a pretty forgiving partial paris system in place.

I'm guessing you don't have Doubling Season in here because of cost, but Hardened Scales is pretty cheap and would do great work.

Darksteel Citadel is going to make the exact same mana as Obelisk of Naya at the same casting cost while also being indestructible and costing like a quarter.

Since you don't have a ton of ramp and you're running a +1/+1 counters theme both Fertilid and Realm Seekers would be useful.

I've been running a Mimeoplasm +1/+1 counters deck for awhile:

I found Hardened Scales did more work for me than Inexorable Tide, and it's quite a bit cheaper to cast.

Gilder Bairn and Vorel of the Hull Clade are nice ways to double your counters.

A deck with that many dudes would play well with Lurking Predators

Generic BUG goodstuff is about as boring a deck as one could make, and running one whose win cons are the most overplayed, cliched combos in the format would get one laughed out of any playgroup I've ever sat with. That said, every meta is different, so to each his own:

In a three color deck I can't think of many times getting a draw off Commander's Sphere offsets the mana fixing Chromatic Lantern gives, especially in a deck with as much draw as Damia has. I can't think of a single time drawing a card off Sphere (or Mind Stone for that matter) radically changed the game, but I can think of a ton of times perfect fixing from the Lantern was saved my ass multiple turns in a row. Not that Sphere (or Mind Stone) aren't good, but I wouldn't run either instead of Chromatic Lantern if I had to choose, especially in three colors.

Not sure where I'd slot it in, and it's pretty half-assed, but Corpse Harvester can be used to snag Sidisi to then snag a combo piece.

Treasure Mage would fetch Triskelion.

Guided Passage is absolutely my favorite card to cast in Riku. Three mana to have my opponent give me my worst land, creature and non-land non-creature is never not a fantastic deal, especially since in EDH every card in your deck should be good and potentially game-changing.

Avatar tribal? Well played, sir.

Ancestral Recall is banned in EDH. Brainstorm or Treasure Cruise is probably as close as you're going to get to it.

I'd run Chromatic Lantern over Manalith. It does everything Manalith does AND fixes your mana, which in a five color deck seems invaluable.

Asphyxiate seems like a lot worse choice than Hero's Downfall in that slot.

Not a huge difference but more often than not Go for the Throat has less limitations than Doom Blade at the same cmc and speed.

Muzzio is a "fair" Arcum, really. You can build a fairly strong Muzzio but it never makes you feel dirty like Arcum does.

I ran Jenara +1/+1 counters for awhile (originally it was Mimeoplasm, I converted it to Jenara, and now I'm converting it back) and I can offer a few bits of advice:

You've probably got too many dudes. Quite a bit too many actually. You're just asking to set yourself up to lose your position and never recover when someone board wipes. I ran 24, and that's a creature-heavy deck for one that isn't running some heavy-creature gimmick. I'd yank quite a few and replace them with cards that support your counter theme.

Gilder Bairn was a bomb for me, as was Forgotten Ancient, Primordial Hydra, Master Biomancer, Kalonian Hydra, Realm Seekers, Spike Weaver, and Vigor.

Solidarity of Heroes can get out of control here.

No Hardened Scales? It's amazing, as is Doubling Season if you can get ahold of one.

Since +1/+1 and -1/-1 counters cancel out Cauldron of Souls almost feels like cheating.

Crystalization seems like a really clunky way to remove a dude. Just run Swords to Plowshares or Beast Within.

Well, that was a strange assumption on my part too because like ten min after writing that I met my EDH friends at the bar and we were bullshitting about the game, and the subject of wildly different metas came up because one guy had been out of town playing over the weekend and saw first-hand a competitive-but-different meta.

Where I play, there's too much indestructible stuff and graveyard recursion to NOT run as much tuck/exile/grave hate as possible. My first two cards in a green deck are Deglamer and Unravel the Aether to deal with Darksteel Plate, Darksteel Forge, Blightsteel, etc. So I see a deck that doesn't run that kind of removal and it looks relatively casual (insofar as one can use that term). But it doesn't necessarily mean that; it could just mean the decks in that particular meta are strong in different ways, with each deckbuilder needing different answers than the ones needed in mine.

I assumed they'd work well here since this looks like a super casual list, Candleabra not withstanding.

That many permanents should find a slot for both Primal Surge and Lurking Predators.

Get thee a Perilous Forays.

Generic comments:

If it was me I'd run less creatures and more ramp and draw. You can only have so many dudes in play at once before wipes ruin your fun. 30 is plenty to swarm, especially if you have draw to get them out faster.

In a two color deck you could probably get away with less land. IMO 38 is plenty, especially with a light curve.

Specific comments:

For a two-mana removal spell Go for the Throat is probably a lot better than Ultimate Price.

I'd run Murder or Hero's Downfall over Flesh to Dust

Dissolve is strictly better than Cancel.

Darkwater Catacombs, Drowned Catacomb, Command Tower and Underground River are all under two dollars, and are significantly better than Dimir Guildgate and Frost Marsh.

A two color deck can afford a few utility lands like Strip Mine (or Ghost Quarter if you're on a budget), Blighted Fen, and Bojuka Bog.

Nykthos Shrine to Nyx is almost always worth it in a two-color deck.

Gravitational Shift would probably generate straight up wins here, while shutting down a handful of other deck archetypes.

With all the evasion you're running Coastal Piracy and Bident of Thassa will probably draw you a ton of cards.

I'm going to guess you're going to change you're mind after some play. There's very few situations I can think of where giving three other players haste for free is worth saving two mana, but it's your deck. Good luck!

Perilous Forays is a bomb in Omnath.

Is giving everyone else haste with Concordant Crossroads worth it when you could run Fervor in that slot?

It's really rough, but here's a generic list of what I might do for Oloro if I built one: http://www.mtgvault.com/doctorhydrogen/decks/oloro-ageless-ascetic-edh-3/

General advice beyond that I can give also applies to my meta, so bear in mind it might not for yours.

Exile over destroy whenever possible. People love indestructible commanders and things, and nothing sucks more than staring at a Darksteel Forge when you're holding a disenchant in hand. For targeted removal I refuse to be told "no". Oblation, Return to Dust, Swords to Plowshares, Path to Exile, Revoke Existence in white, Deglamer and Unravel the Aether in green, Chaos Warp in red, Sever the Blood line in black, etc.

Run things that do multiple things whenever possible as well. Beast Within, Chaos Warp and Oblivion RIng can deal with so many different problems. Maelstrom Pulse is a great removal spell but it can also hit a token swarm, as can Sever the Bloodline. I run Nihil Spellbomb in my Glissa deck over Tormod's Crypt for graveyard removal because the with Glissa's recursion ability I can also use the Spellbomb as a minor draw engine if need be.

Run answers to problems. Obviously not every color can answer everything but one way to handle enchantments won't cut it when you're running green. Run board wipes, targeted removal, graveyard hate, etc.

Get more gas. That can take the form of tokens in a token deck, graveyard recursion in a grave deck, or simply draw. Run more than you think you need. I've never heard anyone say "man, I'm drawing too many cards/have too many tokens/am replaying too many spells from my graveyard over and over" but I've seen plenty of people with an empty hand or board hoping to topdeck an answer.

Reassess your deck on and off. You don't need to be a freak like me who logs all his deck changes in an Excel spreadsheet, because that's will make your wife point out what a colossally obsessive nerd you are, but you should make tweaks. Little stuff adds up. Upgrading that Diabolic Tutor to a Demonic Tutor in January might not be a big deal that crops up that often, but when you do a better job balancing your lands in February, then add two better cards from the new set in March, then add a cool reprint from Modern Masters in June, then add two more draw spells in July, then upgrade from a Ghost Quarter to a Strip Mine in August, and suddenly those eight or ten changes that only make a difference once in a while are numerous enough to make a difference twice a night.

Make something cool. I've built all kinds of decks, but at the end of the day the ones that stick around are the ones that feel like they are my unique creations. The first time someone sees me play an all-deathtouch deck or sphinx tribal they almost always comment on it, and winning with decks like that to me is 100x more satisfying than winning with some generic list I copied from the Top 10 most OP EDH Decks! thread on mtgsalvation.com.

Hope that's a start for you.

It depends wildly on the meta you play in, which is generally speaking is the group. Mine features players who all merciless tune their decks to make them as tight as possible, but who also don't run combo or mass land destruction, and who mostly build with a theme in mind. The first question people ask when they see a new deck is "what does it do?" and they usually want an answer besides "it's a bunch of good cards". People also routinely disable decks if they wind up being too problematic. For example I took apart a Merieke Ri Beret deck because it caused games to drag forever because it made people not want to play stuff knowing I was gonna steal it.

That's my meta, though, so if yours is different you're probably going to want to build to match how those people play, whatever style that might be.

That said, were I building Oloro I'd find a way to use life as a resource or use the lifegain in ways that synergize. I'd probably start by running every single extort dude, and then fill gaps with extort-like guys like Bloodbond Vampire or Agent of Masks. Maybe run some things to do with the life like Slaughter. The key to life gain I've found is to not show it off. The guy at 70 life paints a huge bullseye on his chest. The guy who is at 38, uses six life for an effect to drop to 32, then life gains up to 36, then drops to 31, then up, then down tends to get ignored. People just see the number on the dice and ignore the fact that you would be at 70 life if you weren't spending it on Slaughter buybacks or using it to draw cards of Necropotence or Erebos or Greed.

Well, you're already doing something more interesting than 99% of Oloro decks, which just sit behind half a dozen variants on Propoganda, gain a bunch of life, then due to a commander or combo without accomplishing anything.

Yeah, sacc outlets have been the bane of my existence so far. You don't want to run too many because they're redundant, but when you need one you f*cking need it. I got stuck on Tuesday this week with like 15 elementals on board, but no way to swing thanks to like 15 Hornet Queen tokens, and the game came down to each of us trying to topdeck an answer. Luckily I had Constant Mists free and it bought me enough turns to his Phyrexian Altar, but man that sucked. I think I might just need to slot in more draw to have a better chance to hit the outlets.

No problem, glad to help :)

People are going to look at you like you're crazy when you play the Bauble.. Then something dies and you bring it back and draw again, and again, and again, and again, and eight cards later people think you're a genius :)