You can't get all the harems in one go due to the restrictions on 2 of the ones Bree is part of. You have to choose either College or Gamer due to what path you take her down.is there a order that you have to do the harem to get them all??
Now knowing this, if you still want to do all the OTHER harems alongside your choice, you should start with the Friendly and the first 2 of the Bitchy Harems. Since you need Emma to be OK with you dating other girls and doesn't get upset if you're dating Palla, it would be most reasonable. After getting past Emma's 70 lp block, you can choose the order you want for the rest, Though I probably recommend either Home or Taming next since one takes a lot of work and the other has strict guidelines, but the pay off is keeping Kylie under control. Finally, I defintely recommend Band last unless you already have the sports car, then Office since it requires you to be in summer to finish.