Well RC is key and I get excited when I get one, but I have seen many times when I would trade it for a decent scanner. I see a fleet coming, but I am not sure where it going until it is too late to get over there.
Construction: Duralloy or what ever my first armor is.
Force Fields: Planetary shield V. This has saved me many times
Planetology: This is a tougher one to me. I hate it when I do not get either +10 or +20. This hurts the Klacs a great deal. Atmospheric is my next pick in a game with UR planets close to my start point.
Soil Enrichment/Advanced Soil Enrichment. I love them, but I can steal and can wait. If I do get +10, then Soil moves to first place.
Weapons: Merculite Missile and then Auto Blaster. I want the missile to use as my force retreat tool.
The blaster as my first real ships killer. With HEF and 3 shots, I can start to chew up those stacks.
Yes late game tech is super, but if you miss some of the key early tech, it will be a rough game.
I dread those draws with no Soil, no +pop until 60. No RC until RC5 or later. No shields until at least XV and no missile until Pulson or later. That can get ugly.