I would suggest doing a foam build first. Pepakura and fiberglass resin is one of the preferred methods but it's difficult to do if you don't have room outside and the necessary safety gear. Plus, from my personal experience, it's not fun to use!! (My next build will be foam!)
You can check out
my build thread to check out how I did the fiberglass. I tried to take many photos to give an idea of each step in the process. There's also many many others here have done the same. ( I based my build on many here but used
longshotx, carpathias and
spitfire22v, very good pictures in their threads--If you're doing a different gear set, just use the search function and try and find other builds with the same gear you're using)
Try making a helmet out of pepakura (or a handplate if you'd like a smaller project, do a helmet if you want to see what kind of time some of the larger pieces take, plus the helmet is cool). The only thing you need for this is 110 lb card stock paper. You can get this at any office supply store. For your first go, I suggest a low temp glue gun.
Check out
halo goddess scaling tutorial, I scaled all my pieces using that method and it was very straightforward.
Try doing the Mark VI Normal Def build. The pieces are easy to construct compared to some other sets. You can add detail to them, and really make them look sharp. (If you can't figure out how to invert the pattern on one of the gauntlets, because one of the files isn't there, just PM me)
This is extremely rewarding hobby but I'm letting you know now it's time consuming! If you need any other advice feel free to message me and ask!