Just when I think I've seen it all on elitetrader.com. Now, someone wants to know about which drugs will help in trading. And this, from a moderator. If you're this desparate, perhaps trading isn't your line of work. Hey, I got some drugs for you: Get up off your ass and jog, ride a bicycle, walk, hike, swim, pray, drink water. Unfortunately, we live in a drug-crazed country. Wow!
You should check out Theanine, which is found in tea. It improves focus and provides a calming effect, which offsets the jittery effect that some get from caffeine. You can get Theanine as a supplement if you don't want to drink tea. If you choose to drink tea I believe green tea is the best choice, as it has many health benefits. If you want to buy Theanine I suggest you check out Vitacost, as they have good prices. Their NSI brand is usually the best deal. You should be able to get Theanine at most health supplement sites. FWIW, it will probably be labeled as L-Theanine on most sites.
FWIW, I'm a physician, but my specialty is not treating psychiatric disorders. If you do not actually have ADHD, the drugs prescribed for it will not help you concentrate. You need a specific neurochemical makeup to benefit from that stuff. Seriously, I know it sounds boring, but the best thing to do is get a full night's sleep: 8 hours. Most drugs mentioned above, including alcohol, will interfere in some way with the ability to do that.