Welcome Chungass! The first thing would be to get some unfolds that will allow you to make foam patterns. Unfortunately it doesn't seem there is
any in the armory (yet), but if you do have Pepakura or Armorsmith, you may be able to unfold them yourself.
What sort of budget are you looking to start out with? At its very basics for making foam armour, all you need is a blade, hot glue and paint. If you want to get more advanced, you can use a knife sharpener/replacement blades for clean foam cuts, a rotary tool to clean up any mistakes and add detail, contact cement to adhere foam together, and a sealant (such as PlastiDip, Leak Seal, or Mod Podge) to fill up the pores in foam before priming and painting. A heat gun is also super handy to shrink those pores beforehand.
When I was getting started making foam armour and props, I primarily watched SKS Props, Punished Props, Evil Ted Smith and Kamui Cosplay. They are great leaders in the cosplay community who can give you a good start.
If you have any more specific questions, we're happy to answer them!
Edit: Make sure that, if you are using chemicals like contact cement, or burning or sanding foam, that you use a respirator and have plenty of ventilation.