Saw you guys come up in my google alerts for nootropics, so I hopped on and registered to throw my two cents in. I've been researching nootropics for a few years now.
Hard work and determination is the single most important factor in just about anything, especially poker. Exercise and the right diet are also very important in terms of energy level and how you're feeling. If you're tired or you're feeling negative or emotional, then you're not going to play as well.
Once you have those things figured out, then I'd suggest starting in on nootropics. They're not a magic fix, and a lot of chemicals are called "nootropics" even if they're not effective at all. There's a lot of supplements that simply don't work. There's a lot of supplements that are stimulants only, and these will give you energy now in exchange for a crash later. Modafinil is one of these that's touted as being amazing, but in the end a tolerance develops and sooner or later you have to pay for it.
In the end, in my experience the best nootropics to take are racetams. They're very subtle, but slowly increase your working memory, allow you to keep more numbers in your head at once, and to be a little bit more accurate. They take awhile to build up in your system, and they're not like a stimulant, so there's no high or buzz, but there's also no crash.
[edited by thazar]