The only supplement you really need to buy? Nothing.
The only supplement you really need to do your best? Whatever gives you a good placebo effect.

The only supplements that have been properly tested to have any effect on training capacity? Caffeine and creatine.
The only supplements that have been shown to help with SNS metabolism and blunting hunger? ECA stack (ephedrine-
not ephedra- 24mg, caffeine 200mg, aspirin 82mg typical dose, 2-3 times daily)
How much protein powder do you need? None, if you eat a proper diet. If you don't eat a proper diet, then powder can help you get enough protein to support your muscle growth. Not judging here, don't get pissy at the word "proper".
The main reason so many supplements get pushed by every magazine and web site you read, is because they are in business to make money, not to be educational! Take any muscle mag and count the number of pages that are ads, including the 80% ad pages with 3 sentences of "article" next to it. Show me a mag that isn't at least 80% ads by volume...