If you didn't play GalCivI, I'd reccomend starting on the "Cakewalk" setting (don't worry, you won't have to submit the score if you don't want to

)
Set the games parameters to small or tiny galaxy size, common stars, common planets, and fast tech. Try to maximize your spending in the area's you want to concentrate on by moving the spending sliders in the 3 categories (Social, Military, and Research) these control how much of your total income is spent in each of the 3 areas. You can also focus a particular planets spending by selecting the "target" icon in the upper right corner of the appropriate box on the top of the main planet screen.
In the start of the game (Colony Phase) I like to put total spending at 100%, and military spending at 100% (Research and Social at 0%). This will help you crank out colony ships quickly and beat the AI to the available planets.
Once there, you'll have to juggle the sliders depending on where you want to concentrate your spending (Military to crank out attacking or defending ships, Research to get more techs to trade with minors or other AI, or social to build planetary improvements)
BTW, you might want to also set the initial game to start with only one or two opposing players. The more you play, the better feel you'll have for the mechanics of the game and you'll be able to raise your difficulty level as you become more adept at dealing with the AI.
I can't overemphasize the effect that diplomacy ~can~ have when used well. You can bribe other races by gifting them techs or money or other things you have a surplus of (Ships, Wonders, etc.) until they get to "friendly" relations with you and you can sit back laugh as you bribe your "friends" to attack your "enemies".
I hope this helps, but I'd encourage you to also join an Empire as this can greatly enhance your enjoyment of the game.