So, you wanna be Tony Stark.

Tony was a Car Nut before being Iron Man. Car tech will teach you about Composites, structures, sheet metal forming and all the stuff that comes with it.

We can hijack this for our purposes. For Costume armor, you can carve a styrofoam block in the shape you want, cast rigid Polyurethane foam in the shape you like, or use multiple pieces glued together to form a mock up of the armor you want.

Then cover it with Linen Cloth and epoxy Resin, then fiber reinforced Bondo. Lightweight, classy, easy, and durable.

Want something for Martial Arts combat? Polyurethane foam for Everything. Substitute Fiberglass for linen, and triple up the layers. Thermoform a 3/8" thick piece of ABS or HDPE plastic on top of that and weld the seams with a rotory tool. Rivet 1/8" thick hardened steel on top of That, and you have a Breastplate that can take swing after swing from a Pickaxe.

Want something Lighter? Wood Veneers can be used to build up Elven armor like this. Epoxy is a wonder material.

The critical aspect here is using each material in it's Strong role, backed up by a heterogenous material with a Strength covering for the other material's weakness. In this case, a stressed skin structure, with a hollow core made of high density foam.

Once we have our structural armor and exoskeleton as a Unit-body, we need a way to Boost it's movements.