Typewryter

Ooh, you know what, I hadn't even considered Vexing Devil! Brilliant idea, I like it~!

Glad to help ^ ^

Off the bat, I would say that Chronic Flooding is rarely worth the two mana it costs. I think you'd be better served replacing it, and the Delvers of Secrets, with four copies of Think Twice.
Next, I'd say you can drop Dream Twist and Duskmantle Guildmage for four copies of Mind Grind. Dream Twist is alright, but its unnecessary, and Duskmantle's abilities are just way too expensive when there are cards doing better for cheaper.
You can also replace the two Codex Shredders with another pair of Fog Banks. Those guys can keep you alive when things get rough.
Nephalia Drownyard is situational at best, you shouldn't be in a situation where you need to pay 2 mana to mill only 3 cards. I'd say cut them for an island and a swamp.
If you're focusing on mill, Jace's Phantasm can be replaced by the awesome Consuming Aberration. Milling a good chunk of the opponent's deck every time you cast a spell is a powerful option for a mill deck.
Far//Away is a good choice. If you're looking for more draw power, you could potentially replace it with Inaction Injunction.

That's my advice, anyway. I hope it helps you in some way, and in the end, I hope you wind up with a deck that works for you, and most importantly, that's fun to play.
-Typewryter

Well first, I'd like to welcome you back to Magic: The Gathering!
About your deck, though:
First, I'd say swap out the Guild Gates for 4x Dragonskull Summits. Same thing, a land that taps for R or B, but it only comes in tapped if you don't have a swamp or mountain, so you can actually use it the turn its played.
Necropolis Regent is stupidly wonderful in a deck like this, and so is Olivia Voldaren. However, I've always been of the mind that it's better to have 3 of one card, than to have 2 and 1. 1-of's are fine, but 2-of's just take up space that could be better used to increase the odds of finding your 1-of. I would recommend either 3 regents or 3 olivia's, but not a 2/1 split.
Falkenrath Marauders is a powerful vampire card. I would recommend swapping him for the Nighthawks. Nighthawks are powerful, but they don't synergize with the vampiric mechanic of your other vamps. In case you don't know him, Marauders is a 3RR, 2/2 flyer with haste. every time he damages an opponent, he gets Two +1/+1 counters. Stacked with rakish heirs and necropolis Regents, they quickly get insane.
Curse of Stalked prey. Oh, I cannot put into words how much I love this card. That is all.
Curse of the Bleeding heart might be of use to you. It saw use in all of my vampire decks. The card makes your opponent lose one life every turn. One is a nuisance. Two is a threat. Three or four is cataclysmic.
Havengul Vampire is a 4 mana 2/2 that gets a +1/+1 counter when he hits an opponent. Pretty old hat, right? But he also gets a counter whenever something dies. Anything. At all. So that's something to think about.
Heirs of Stromkirk continue the powerful vampiric mechanic you're seeing, with the added bonus of Intimidate.
Markov Blademaster. Vampire, 1RR, 1/1. Gets a counter whenever she hits someone. And she's got Double Strike. I think you know where I'm going with this. Can you say +2/+2 per round~? goes in as a 1/1, hits for 3. Goes in as a 3/3, hits for 7. 4/4, hits for 9. Simply beautiful.

That's about all the advice I've got concerning Vampires. Whether you take it or not, I hope it helps you in some way, shape or form. You were playing 7 years ago, I just started about 2 years ago, so I'm certainly no expert, I'm just sharing what I know works for me.
I hope my advice was helpful, and no matter what, I hope you have fun playing again!
-Typewryter

Looking over the deck you've got here, it seems to lack focus. Not that the cards aren't good cards, but they don't really compliment each other very well. Sticking with your goal of "Winning as fast as possible," I've put together something that should serve your purposes. I've cut it down to mono-green:
- 4x Kalonian Tusker (GG) Creature – Beast (3/3)
- 4x Brushstrider (1G) Creature – Beast (3/1) Vigilance
- 4x Battering Krasis (2G) Creature – Fish Beast (2/1) Evolve
- 3x Garruk’s Horde (5GG) Creature- Beast (7/7) Trample, Play with the top card of your library revealed. You may cast the top card of your library if it is a creature card.
- 3x Skarrg Goliath (6GG) Creature – Beast (9/9) Trample, Bloodrush 5GG: Target creature gains +9/+9 and Trample until end of turn
- 4x Elvish Mystic (G) Creature – Elf Druid (1/1) T: Add G to your mana pool
- 4x Gyre Sage (1G) Creature – Elf Druid (1/2) T: Add G for each +1/+1 counter, Evolve
- 4x Gatecreeper Vine (1G) Creature – Plant (0/2) Defender, when GV enters the battlefield, you may search your library for a basic land or gate card, reveal it, put it into your hand, then shuffle your library
- 4x Axebane Guardian (2G) Creature- Human Druid (0/3) Defender, T: Add X mana in any combination of colors to your mana pool, where X is the number of creatures with Defender you control
- 4x Advocate of the Beast (2G) Creature – Elf Shaman (2/3) At the beginning of your end step, put a +1/+1 counter on target beast you control
- 22x Forest
Now, let's break it down.
Mana: Mono-Green. Going single-color means you don't have to worry about whether or not you have the right lands, only if you have enough. With 22 forests, you should draw them regularly enough to put down the main creatures of your deck. Add in the Gatecreeper vines to fetch lands, and missing forests shouldn't be a problem. Next you've got your mana-producing creatures: Axebane Guardian, Elvish Mystic, and Gyre Sage. We'll go through each in order.
---Axebane Guardian. Early on, this card will only tap for one mana, which seems low for a 3-drop card. But each one you put out increases the mana they all produce, and your Gatecreeper Vines will do the same thing. Late-game, each Axebane will be tapping for two, or at least three mana each.
---Elvish Mystic. Doesn't get simpler than this. Play one first turn, play them whenever you can. Only one mana to put down, and he acts like a living forest. Classic.
---Gyre Sage. Now this is where the fun starts in this deck. When he first comes out, he won't get you any mana at all. But with each heavy hitter that comes out, this guy gets stronger, and as he gets stronger, he puts out more mana. Eventually, he'll be able to join in and swing right alongside your biggest beasties.
Creatures: As you can see, this is a beast-focused deck. Now you have a number of low-cost beasts,Kalonian Tusker, Brushstrider, and Battering Krasis are the cards you'll be swinging with the most often, simply because they're cheap, and you've got four of each. However, the rest of your creatures are special, and we'll be going over each of them individually: Garruk's Horde, Skarrg Goliath, and Advocate of the Beast.
Garruk's Horde. At Seven mana, he's a big fat fatty, but if you're fetching lands and playing your mana creatures, he should come down by turn five or six. This is where you'll start picking up speed. While this guy's out, you play with the top card of your library revealed, and if that card is a creature card, you can cast it right there, as long as you could cast one at that time. If you've got 4 Forests, a Gyre Sage with 3 counters, a pair of Axebanes, and a mystic, thats 12 mana right there. You can just start flooding the field with beasts as soon as they reach the top of your library. Top card's a Battering Krasis? Play it. 9 mana left. Underneath him is a Kalonian Tusker? Play it. 6 Mana left. Advocate of the beast next? 3 left. Garruk's Horde will allow you to tear creatures right out of your library, and of course, all of your mana creatures (obviously) produce mana. Which means he can even speed up your ramping, which can lead to more creatures, which leads to more mana which leads to more creatures, etc. etc. etc.
Skarrg Goliath. Oh boy. Ohhhhh boy. This guy. He's eight mana, so if you can cast Garruk's Horde, this bad boy isn't too far behind. At 9/9 and trample, you may be tempted to rush him out, but hold on to him when you can. For one mana less (5GG) you can discard him to give another creature +9/+9 and trample until end of turn. Once you've got beasts up and you're ready to swing, let 'em rip. Wait till your opponent declares blockers, then tap down 7 mana, throw this guy in the graveyard, and watch your opponent cry.
Advocate of the Beast. My personal favorite in this deck, this guy's the reason I went with beasts. Just look at him. 3 mana, same cost as most of your beasts, which means you can put him out right alongside them. Every turn he's out, something gets bigger. And bigger. And bigger. You actually cast one of your Skarrg Goliaths? Watch your 9/9 become a 10/10. An 11/11. A 12/12. With trample. Hell, let's spread the love; give a counter to a different creature each turn. Put down multiple Advocates, get multiple tokens. Simplicity at its finest, beautiful in the extreme.
Of course, you can switch things around a bit if you like; one idea would be to throw in the new Garruk, Caller of Beasts. Maybe take out the Skarrg Goliaths for him. Putting creatures in your hand and playing them for free is great, and his ultimate lets you flood the field like never before!
If you find the deck running too slowly and getting cut off early, fog can help keep you alive while you set yourself up and ready your mana base for the absolutely obscene spending you'll be doing with Garruk's Horde.
Enlarge is a good way to hurt your opponent, doubling the power of Garruk's Horde and forcing a block, allowing you to do some serious damage to their life or their creatures, maybe even both.
A Kalonian Hyrda, if you can get one (Mythic and all) would synergize beautifully with both Gyre Sage and Advocate of the beast. Every time this bad-boy attacks, you DOUBLE the +1/+1 counters on every creature you control. That means double mana from Gyre Sage, Double the power of your buffed creatures, and double the pain and misery of your pitiful foe (Bwahaha)
These are all just suggestions, in the end, what really matters is what works for you. I saw an open call for help, and I responded with my two-cents. I hope that the advice and information here helps you in some way, and I hope you can put together a deck that you enjoy playing, because in the end that's what matters. Magic is about having fun, never forget that!
-Typewryter