they don't gain exp doing missions but uses bios as exp chips
1-40 costs 131 bios
40-45 i think it costed 151 (kinda forgot but it was around 150)
45-50 costs 351 bios
to rank them up you need black anti matter
50 rank1 black anti matter (this is what you get from the world boss as drops, usually around 40-50 per drop) fuses to 1 rank2 black anti-matter
2 rank2 black anti-matter > 1 rank3 B-AM
2 rank 3 B-AM> 1 rank4 B-AM etc.
to rank up from 1* to 2*, you need 6 rank2 B-AM (300 rank1 B-AM)
2* > 3* = 5 rank3 B-AM
3* > 4* = 4 rank4 B-AM
4* > 5*= 3 rank5 B-AM
5* > 6* = unknown yet but probably 2 rank6 B-AM
gears past level 15 don't cost a bio, guks and debris but worse .... 10 black anti-matter, 5 guks, 3 debris and 80k per attempt