that's cool, once I get better gear I wouldn't mind playing with you guys, right now I only have Fang prime as worthwhile weapon, can also make lex and paris primes but not until I reach rank 8, and even managed to completed Limbo prime.
Sounds like you're making good progress! Post your PSN, and we'll get you a Reset Era clan invite.
Chroma, Rubico and Gram Prime were all relatively easy farms. If you're not in a huge hurry to get them, just keep an eye on Cetus bounties, because most of the relics are in that rotation. It's especially useful for Axi relics, which aren't on any rotation A as far as I know.
Chroma: I think it took me 3 runs for Chroma's common BP and 3 runs for his rare neuroptics. The only relic I had any trouble with was the Lith C3. I got my first two in Cetus bounties and my third in ODD, but it took a few runs.
Rubico: I got the receiver and stock randomly while running defense fissures for Lith C3 relics. The Barrel took two runs (relics from Cetus bounties), and the BP took three runs (relics from Helene Saturn).
Gram: I think I got all parts on the first run (might have been two S8s). Axi O4 came from Cetus, Neo G1 from Hydron Sedna and Meso S8 from Helene Saturn.
Good luck!!