First mastery lab?

I have RPC, Cash & Damage unlocked. Will finally have my first q saved up today. Which one should I shoot for first?

Damage: later this week I’m respec-ing to FB to get assmods. Feel confident that I’ll make it (since I’m at T18/W195) and I think 1st level of DMG will help me reach this goal.

Cash: I am suffering with rerolls. 2/4 mods just reached lv. 161 and the other 2 are closing in fast. I stress out more than I’d like about getting the substats I need for farming and tourney/milestone

RPC: probably the best one since it helps everything

Basically, I’m between DMG & RPC. Any thoughts?