well u can get all cards without paying money for it, the chance is probably just lower to get certain cards u want or something (as i said, i didnt played the game yet, but thats what i did read)
and that people which pay real money dont have any huge advantages on a player which didnt.

u can play the game without paying for it, and even on a high ranking. you may just need some luck with the boosters u buy/get from the money u earn by playing. so i dont really know what u mean.