I've done a bit of research, reading around, saw what other people are taking, but what kinds of things should I avoid so that I don't end up sabotaging myself?

I've seen that caffine is mentioned a lot. Please say i don't need to worry about that one. I'm a mountain dew junkie. I'm also a very light smoker, and I exercise frequently, but usually just stretching and a mid-tempo long run (4-5 miles, 7-8 minute mile pace)

Ok...you don't need to worry about that one!!

Seriously, you don't, most of us live on coffee I think, and its an old wives tale that it stops NBE

Good to hear. Any input on what I really should avoid, then?

Nah, not really. I eat whatever I want.
It is said that chocolate isn't a good idea because it affects the natural dopamine in the brain, but even then as long as you dont live on the stuff I can't see any harm in the occasional treat.