If you don't mind spending a little on the game, then when a roulette is active it is worthwhile to buy some of the $1 for 30 roulette tickets. Exclusively focusing on getting AS soul bingos makes it way easier to lvl 90 collab units (seasonals too, but those can at least be grinded in Soul Quest). If you are lucky then you'll also get whatever featured unit / card on the roulette is as well.Also... reading the above posts, I really need to level up my Kazuya. I even have his card. He's just sitting around at lv60 not being used. I wish I could do his soul quest.