"trade or upgrade planets"

Well, always at least get yourself in the Green on these planets. If it's in the heart of your planets i.e. your opponent won't get to it for a long time then definitely. I'm always wary of building trade ports very early, within the first hour that is, because tradeports take time and plenty of credits/resources to make them.

My order is up the planet, get a fleet that can defend the planets, and then tradeports. You can do these simultaneously, but be wary of building a lot of trade ports if you think you may soon be attacked.

I agree! Planet upgrade first...otherwise you'll lose a lot of money very quickly.