Buildings, energy, hull, defense, in that order.

rank?

Dont spread your research around finish the whole tier

no spread it around, dont finish the whole bar when it comes to ship stuff. Costs and upkeep rise exponentially while benefits linearly. For the same price and upkeep of for example, weapons if you are far into it, you can upgrade your defenses and hull to equalize or surpass the effect of just 1 tier of weapons. Do get buildings up to speed when you can. The investment is far worth it in the beginning.

I think he meant research an entire bar first (eg. finish Micro-singularities before researching anything else)

Structures, scanners, hulls, defenses, energy, weapons in that order.