Goblin

I'm not sure if you're open to suggestions, but here's my 2¢. Chances are you're already aware of everything that follows, but if not, I think you should consider a few options which have always worked well for me.

In my opinion, you really need to add a way to sacrifice Goblins for mana. For example, if you add a Skirk Prospector, you can sacrifice 2 Goblins to the Skirk Prospector for 2 red mana and then a 3rd Goblin to the Siege-Gang Commander's ability. Otherwise, you'll be very limited in the ways you can win the game (mass attack with pumped-up Goblin Piledriver + Loyalist for trample) and rather easy to counter (any mass removal).

You could also want to add a Goblin Sharpshooter (or more), which works very well with Skirk Prospector and Siege-Gang Commander, if you decide to use those too. Basically, you'll tap the Sharpshooter for 1 damage, sacrifice a Goblin to the Prospector for a red mana, which will untap the Sharpshooter, tap it again for another damage, sacrifice another Goblin for another mana, Sharpshooter untaps again, retap for a 3rd point of damage, sacrifice a Goblin to the Commander for 2 damage, which untaps the Sharpshooter yet again, etc... This effectively counters mass removal (sorta...), since you can sacrifice your entire army before it gets annihilated and at least get some damage done.

Another very strong option you might want to consider (as an alternative to using Aether Vials) is to splash into Green, for Food Chain. I've been playing Food Chain Goblins for years and it never lets me down. Never. It basically allows you to sacrifice any creature for 1 more mana of than its converted mana cost, and works very well with Goblin Chieftain, which reduces your goblins' mana cost to begin with.

I played my Food Chain Goblins deck, yesterday and I had 3 Chieftains on the battlefield along with Food Chain, at some point in the game, so my Goblin Recruiters would cost me 1 Red mana to cast, but grant me 5 Red mana when I sacrificed them to Food Chain. Long story short, the Recruiter was not only having me draw tons of Goblins, but also allowing me to have tons of mana to have everything I cast enter the game. For that matter, Incinerators, Matrons and Ringleaders (along with Mudbutton Torchrunners, check those out) are the best creatures to sacrifice to Food Chain, since they're almost useless once their main ability resolves.

Finally, since Food Chain only costs 2G, I have no problem running my deck with 18 lands, although I use 4 Skirk Prospectors so I can rely on them in case I'd get mana-starved for some reason.