Here's Arthur's tip from the official guide:
The more skilled a researcher is, the more points they produce. Higher levels of Science technology increase the number of tech points that each researcher produces. Keeping a fire lit gives a small tech point bonus, and, finally, collecting missing lab pieces gives a bonus for each piece retrieved. All of these things combined make for very productive researchers!
Having a dozen or more peps working in the lab helps too.
Regarding upgrades, each person has their own preferences in what works best for them. I started with the cheeper upgrades and worked my way up.