To start I'm a free user. You're overlooking the rare cards like trainer yes the cost to level up to rank 2 or 3 is a pain and a long grind but it will be a big help every map gives viagra at A8 it's 60% chance to get 385. The trainer is like lady Vamp for damage a lot of rare cards can help a lot and can be ranked up faster than epics. the Egg card give the bomb skill that can help block out fuck is a good skill to sadly I've only seen epics fusion having that one cuz rare fusion only use the first skill on the two cards. I'm farming A8 the thing is you have to to pay it can be time like me (I got on at the Bata) or money it's on you. I'm farming A8 before I go to A9 my mains are Lady Vamp R1 x2 and Trainer R1 R2 + Thinker R1/ Ring R2 RMax and Secretary R1.
p.s. for others cards start at rank 0 and it's not a good thing to rank up all the time but maxing out every rank is cuz you get bigger bonuses from fusion the more level your card has.