You don't need to purchase credits to get items. You can do a weekly challenge, get a prize drop, and use that new item to trade. You still get items I believe while leveling up and doing the battle pass as well, so it should still be doable to trade. This trophy list should be 100% able to be done without paying. I'm 2 trophies away from 100% and I haven't spent a single cent, although I did get the game from ps plus.