Change your side characters a lot, to equally grow their exp and affinity and if you want to see all heart to hearts and affinity quests try to max out Lao early in the game. Also try to raise your mechanical level first so you can probe as much of the planet as possible as...

early as possible, with research probe you'll earn the most money, mining probes give you miranium and precious minerals, selling the last one can get you lots of money too. Oh yeah, you can raise affinity easy by doing basic missions from the terminal, those are also repeatable.

Enjoy the game and good luck!