That is a tough one, if you're going for accurate mayan/aztec they rarely wore much in the way of armor, mostly ornate headress that served as helmets, some would wear, skins much like the animal their group identified with but that woudl be expensive to try and pull off.
If you just want a more basic barbarian kinda look with some aztec flair many craft stores sell little bags of leather scraps. Riviting or sweing those onto belts can create some pretty barberous armor, add in a headress and some feathers or faux fur and you can have some armor at a decent price that woudl capture some of the look you want.