U need cateyes to get other cats that are not basic with the rarity cateyes
From left to right:
Special catseye, rare catseye, super rare catseye, uber super rare catseye, legendary catseye. Each one increases the limit of upgrade by 1.
I'm user rank 3765 and most of my normal units arent even above lv 25 i keep getting the normal unit every time i do a normal cat capsule so i feel you.