Here's Arthur's tip from the official guide:
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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.
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It isn’t about the journey
its about the destination