Probably a good but not the BEST idea, but sort your units in priority (High-Low) and level top-left to bottom right. I've noticed that units with higher rarities PROBABLY have better stats than those in lower rarities. Hit that normal gacha every day and see if you can get four-stars, and I'd say to throw out the three-stars that don't/wouldn't make it into the 3rd or even 4th squad.