I can't actually tell what you are asking about material for. A cage on the stock frame? The suspension links? I see you may be replacing the frame as well.
People usually go stronger than stock. Try to get a measurement on the stock frame in several places. Understand that adding height to the frame will add strength faster than adding width (like taking 2x2 tube and considering going to 2 wide x 3 high or 3 wide by 2 high, the taller profile is stronger). Entropy is right on the money with a good starting point for frame material. I agree.
For links, 2x.250 lowers and 1.75x.250 uppers is a good moderate place to start. If you are going to slam the thing into rocks, go bigger. But it depends on your link length, double the length, double the bending stress with the same load. How long do you think your links might be? 2" OD anything is flimsy on a 60" link. But it is way overkill on a 20" link.
Cage material is nearly always 1.75x.120 DOM. 2.00x.120 is a big step up in strength. Your stock cage (at least on a late TJ) is about 2.125x.120. I think the engineers did that because the stock cage has so little material and triangulation they had to use a crazy beefy material.
Here is a tube strength calculator my company developed: https://www.roguefab.com/calculator.php
It is great for running numbers to find out which materials are stronger and things like that.