@mere_immortal I'm no expert (I think I've only built like 2 or 3 Gundams in my life), but I will say that it's worth shelling out the extra 10-20 bucks for a Master Grade kit (over a High Grade). I found the High Grade kit to feel sorta cheap, and tough to pose. Master Grade is also bigger so it's less fumbly to build. In terms of specific kit - just browse around and pick one that looks cool! There are a lot.
Good info! Was wondering about the HG/MG stuff and how different they were, will look at the MG stuff!