well, your two most important supplements IMHO to have are:
1. a protein powder (like Truemass if you're bulking up)
2. a multivitamin
others will argue this supplement and that supplement being needed, but those two included in a clean diet and good exercise program will cover the basics.
there are different kinds of protein powders, too. usually you can just read the ingredients and you'll see them:
1. whey protein (i.e. Truemass) is the fastest digesting and is best used for pre-workout and post-workout shakes.
2. casein protein is a little slower to digest, so is great to use before bedtime.
I'll let the other more experienced members suggest other supplements to use besides the two that I suggested because I only use 4 supplements, including those two.
the other two I use, and I don't know if anyone else on this forum has tried it, is a Niacin pill + a Chromium Picolinate pill with my pre-workout shake.
hope this helps!