You can unlock 20 pieces of armor and then spend 1000 silver after. To me, I will find 20 pieces quickly. Just B line to my favorites. I don't know if there is 20 that I MUST have. Probably 3 sets of helmet, arms, chest, and legs = 12.

Then 8 cloaks. I think it's enough. You?

Also remember, one piece is an exotic slot. When I first saw it and then looked at collections. Which btw, go look at your collections. It feels just fine. For me there definitely wasn't more than 20. I have my "for sure" set or two and then multiple "single" pieces.