well before any of that, i'd put up a tracklist and consider in advance what tracks sound good together, aswell as putting variety in there. Second, i'd make sure all the tracks have the same tempo (because in FL it's kind of complex to do so). i'd adjust the final tempo difference as a whole, in an automation (master tempo).
When working in FL you'll be working in the automation field, dropping all tunes in there, and when "mixing", make use of two workways: cutting off audio clips to where you want to track to end and automating the low frequencies (so they don't conflict), it's quite easy to do so with an equalizer
