Hi,
I'm by no means an expert but i'm willing to offer my thoughts. if nothing else others might pile in and tell me where i'm going wrong.
Luckily he has a fairly straightforward costume so it just depends how accurate you want to be.
Also there's a few questions to ask.
firstly what kind of skill set have you got? can you sew, work with metal etc.
Also it depends on your body type. he's a pretty big guy. So you can either bulk up or build a muscle suit. or ignore that part altogether.
So i guess as a starting point you need a slim-fit yellow t-shirt. easy enough.
the thunderbolts can be done in a number of ways. Professionally printed, transfers, fabric paint or even a sharpie.
for the pants i'd begin with some sort of combat pants for convenience. the detail on the side can be done either by sewing on additional fabric or using puff paint.
For the arm pieces I'd be inclined to start with a pair of of fingerless gloves and some sort of fabric sleeves. I don't really know what they would be made of in the actual costume. You could take the sleeves from a regular long t-shirt or you could use some sort of leggings that have a vinyl kind of effect. stitch these together so that you have a continuous piece for each arm.
I'd then use something like EVA foam to make the rings. you can paint this with something like plasti-dip to give them a smooth metalic finish. I'd do the same with the belt.
these are just some broad ideas i had . If we knew what kind of accuracy you were going for and how you'd like to approach it you'll get better help.
good luck with it.
