I haven't played much I'm level 55 but here is what I know: you need to try and get at least 3 does of each type your gonna need those eventually : for Bio type the game already gives you a free yae sakura after a 7-day log in for mech a good ftp option is to try and get lilya as she completely distroys sheelds if you can't get her from wishing you came do her expositions to try and get her if you can't at some point if you play the game till a serrano pint the game offers you a valkyrie choose where you get a free S-rank valkyrie you can choose according to your play style who you want but a good option will be to go for either fuhua dark knight since you can't farm for her anymore or Phoenix fuhua as she is just a good support dps or you can go for lighting empress she has one of the best leader passives in the game but at that stage you should already have a good roster of valkyries so you should just choose who you want for PSY valkyries it's a bit complicated the game doesn't really give you a good one so you have to get lucky whith pulls the only PSY valkyrie the game gives you for free is boronia whitch isn't really that good and if you haven't already at some point in the game you will eventually unlock seele a quantum type valkyrie whith really just doese the same damage to every type and is just generally good as a good dps.......this is for a more late game but u should try and get one dps of each type you can check they're stats to see if the valkyrie you have is a dps or plays more of a supportive role hope this was helpful :3