GREAT QUESTION! Man, so many of us are taken advantage of by the supp industry. What do we really need? The truth is, we don't need any of it. But there are some good things that will help. And alone, some things may not make or break you, but when combined, it can give you an edge that you may not have had otherwise. Here are my thoughts on a few of the more popular options out there. These are the things I use

Protein :

I stick with whey iso. Its very effective. Its plenty fast post workout and it can be mixed with fats to slow digestion at other points in the day, like your last meal before bed. Whey is an easy way to add to your total daily protein without a lot of work. The bigger you get, the higher your protein needs go, and the harder it is to eat all solid foods. Post workout, I will use a whey iso shake to get aminos in my blood fast. Then go to solid food, within 45 min

Fish oil and multi :

I'd consider these basics. You want to use high quality multi's and get your fish oil in every day. I would suggest these things to anyone, not just someone that wants to excel in BB

Creatine :

Its cheap as dirt and it works, so why not use it? I just go with a cheap creatine mono and take 5g pre, 5g post. I cut it out a month from a contest, otherwise, I run it most of the year. I take time off when I run out. Usually a few wks off at a time, but run it for most of the off and on season

Carbs : 

This is an interesting one and one of hot debate right now. Highly branched cyclic dextrin is the new hot thing. If you are doing long workouts, like over 2 hours, and your diet allows for the carbs, they seem to work very well. The new intra workout shake is HBCD and a fast protein source or EAA. NOT BCAA, but EAA. This shake may be less useful to guys that train for shorter periods, but for us volume guys, they are making a difference. You can also use a high weight carb like waxy maze to save money instead of HBCD, but it isn't quite the same quality. This plan works very well for guys using insulin. This is the evolution of using dextrose post workout. Dex is cheap and its better than nothing, but IME, it is inferior. If money is tight though, this alone isn't going to take you to the next level. It may just be one piece of the puzzle thought. 

Proworkout :

There is no real need as far as direct muscel building effect, but I'll be damned if I don't train harder and work longer when I have a good preworkout in my system. The more pumped I feel, the more likely I am to get in an extra rep and if I'm working harder, I'm growing. 

Thats it. These are the things I use. I pull the carb drink during my diet, but the rest stays in for most of the year.