I'd pick a single pattern and and buy the materials just for it, most of the basic stuff can be used in multiple patterns and styles. Repeat this with a few patterns and you will have full kit before you know it
I think this is really good advise. When I started, I thought I needed every color of floss that they sell (and i got most of them at about 35 cents a piece). And something I didn't even think of at the time, what you need depends on where you live (and what you fish for), and how you want to fish for it. For instance, their aren't any salmon living near me so I haven't tied many salmon flies, besides some salmon streamers which I have caught bass on. And I think fishing dry flies is a little more fun for me--and I know I prefer to fish dry fly sizes 10 or 12, possibly including 8 or 14. I'm big on terrestrials. So once you have parameters like this, it makes your purchasing decisions easier. The people who assemble (regular) kits don't even know what type of flies you want to tie. Once nice thing these days, is that you can get your hooks in bags of 25. In the 70's, you usually had to buy a box of 100. I suggest you buy at least 2 sizes of dry fly hooks, and likewise some hooks for wet flys/nymphs/streamers, depending upon what you want to fish. If you want to tie a bass bugs, you'll need a different hook (s) for that . So, amusingly, the answer to the question of what you need to buy, depends on where you intend to fish (at least it does for me, I guess some people will tie flies they will never use, just for the sake of doing it). Have fun! P.S. As far as thread goes, "black" goes a long way. If you want to tie (spun) bass bugs, you'll need some heavier thread. If you want to tie a size 18 fly, you'll probably prefer a lighter thread. I feel compelled to add, in case it's not obvious, that generally speaking, a larger fly is easier to tie than a smaller one of the same type. So there is no reason to start too small. A size 12 dry fly seems plenty small enough (for me!) It's probably preferable to start with a size 6 or 8 streamer, and build up a little confidence... If you are trying to "match a hatch", your requirements may be more severe. But, IMO, starting too small will only lead to frustration.
Edit: Oops, I see the OP posted his question in February, so he is probably catching fish on his flies by now!