http://www.examine.com
That should be your source for straight up supplement knowledge. No bro-science. Actual science.
That being said, here's my take on supplementation. It's not very hard nor complex, but it can be hard to wade through the marketing machine that wants you to buy all of it.
First realize that they're supplements, not replacements for actual food. Eat actual food. Whole foods, at that. (no, not the store. I mean generally not sh#t that comes in a box)
There are really only a few that have actual measurable benefit. None of which you actually *need* to achieve your goal. They can help just a teenie tiny bit.
First, protein powder. I actually consider this more of just quick and easy food than an actual supplement. I use it when I need some quick food and don't have time to actually warm up something.
Second, creatine. There is undoubtedly more research done on creatine than any other supplement. Studies show (check out examine.com) that it does actually increase performance along with some other actual benefits. It's cheap as hell too, at least in the US. I take about 3g a day. No need to load it or do any other sort of protocol, but you can if you want. Once you read up on what it actually does, you can make a decision on whether to use it or not. Oh, and don't be fooled by fancy creatin (buffered, etc). Plain creatine monohydrate is not only the most studied, it's also the cheapest.
Here is the first of three parts on how creatine works. I believe it to be accurate. Kind of interesting if you're a dork, like me. http://athlete.io/3562/the-ultimate-guide-to-creatine-supplementation-part-1/
Third, vitamins. If you eat a varied diet of mostly whole foods, you probably don't need to bother with a multi but take it if you want.
Most people are deficient in Vitamin D in the northern hemisphere, especially in the winter. You know, when the sun is friggin gone for months or only comes out when you're inside.. So, I think it's a good idea to take 1000 to 2000IU /day. Liquid or liquid caps.
Fish Oil. There are studies that show some benefit at the 1-2g / day level but that's about it.
BCAA's or branched chain amino acids. I like these in spots especially if you're eating at a caloric deficit. All protein, hardly any caloric load and doesn't really require any digestion to be processed. I use them occasionally but never really worked them into a routine.
Hope this helps. Check out examine.com though and come to your own conclusions.