I'm trying to play on normal now, with the default settings, and 5 enemies... I just have one problem.
I suck.
I never know what to do. I always take research as the top priority - which leads to my planets being very empty, because I never know what to build on them, and I'm putting 70-80% of my funds into research. On top of that, I always forget to start trade routes, build a little army for protection, and things like that.
My problem is, I just don't know how to handle everything. I think I lean too heavily on one thing, and completely neglect the other. I also never have any clue how to build planets.