So in the realm of 3D printing there are 2 different worlds, Resin and FDM.
FDM is what most people think when they hear "3D printer", it heats up plastics from a spool and puts it onto a bed in a very controlled manner. It's quite like a computer based hot glue gun.
Resin is more of a small-scale/detail based style for most people (of course this isn't completely true as I'm SURE some people would use it to make suits, it's just much less common). Resin is useful for smaller prints that need to be more detailed, such as wargaming miniatures or small components for suits that require detail that FDM printers just can't achieve.
Assuming you're looking for an FDM printer for printing armour pieces and the like: The model would really depend on your budget, personally I started out on the Creality Ender 3 but I would recommend one of the newer models/variations or other options from Creality like their K1 or Ender 3 V3. One of the best options you could go for would be a Bambu Lab P1P or P1S, they're some of the easiest machines to run and are very fast to print.
Though you don't want to discount filament costs and maintenance time from your decision to buy a printer. I've got a pretty quick printer myself and it EATS filament, over time those filament spools add up
. You'll also want to learn how to maintain and fix any problems that come up on your printer, they're not as "plug and play" as some people might think.
It'll require an investment and a bit of learning but once you get it right it pays dividends!
Feel free to ask any other questions you may have