Yup it can get really confusing, but as others have said use what you have. One of the big challenges when starting out in tying--- or restarting-- is learning what are acceptable substitutes for stuff listed in recipes. That goes for hooks as well as other materials.
Just pay attention to the different properties of hooks so you end up with something that will work for you.
nymphs and wets on heavy wire hooks will sink faster. Use light wire hooks for most dries and emergers and nymphs you want to fish high in the water column.
Shank length-- you might be able to get a way with a larger size 1xl nymph hook instead of using a 2xl or 3xl nymph hook in a smaller size. Use differences in shank length in different models of hooks to fill in any gaps in your hook inventory.
For many years, Mustad was the standard, and I more or less grew up with them and still use them, so i'll list the ones i still use below. But there are many other choices available. Here's a hook chart that might help to get equivalents in recipes you see, and you can use it to translate it into your preferred hook brand/s:
Fly Hook Comparison Chart
dry flies standard length, extra fine wire. For dries and emergers and nymphs you want to fish high in the water column. Mustad R50-9484. The Tiemco 100, a light wire dry fly hook with a wide gap is very popular and doesn't really have a Mustad equivalent.
wets (soft hackles and winged wets)
Standard length and heavy wire Mustad 3906
Nymphs 1xl or 2xl
Mustad 3906B (1xl heavy wire, sproat bend) or 9672 2 xl (standard wire, perfect bend, I use this with beads)
Bugger, muddler (and stonefly or hopper dries with foam bodies) 3xl
Streamer 4xl (can also be used for above)
Mustad 79580 or 9674 (I also use a size 12 4xl 79580 for Eastern Green Drake dry flies. Because of their large size (standard 6 or 8), using the smaller size 12 4xl is actually lighter in weight (thinner shank) than a standard size 8 dry fly hook, but is the right length.)
Scuds (and caddis pupae, emergers)
I use Tiemco 2487, a light wire 2xshort hook for emergers, and caddis pupa that I want to fish in the film or close to the surface and Tiemco 2457 ( the same hook in heavy wire) for scuds and caddis pupae that i want to fish deep. Both hooks can also be used for nymphs for a different look.