The pentastar alliance is probably your best bet, decent starting position, can field a fleet of capital ships and carriers, ground force is decent enough without feeling like somethings missing, and starts next to easy to conquer planets and factions such as warlord zinjs, empire of the hand, and the empire for easy planets to grab.

One of the smaller historical campaigns might be best. Less enemies to worry about, smaller planet number, etc.

well i would say maybe dont do a campaign if your a beginner if you dont want i sujest do skirmish untill you get the hang of how strong the ai is but i would say try all of them until you find one that you like

Skirmish is very different from campaign and while you might get battle experience it doesn't teach you anything regarding campaign level content.

I've heard the Thrawn Campaign is a pretty good starting point. The NR and Empire start out relatively evenly matched and you only have the other faction to worry about when it comes to attacks.

Cheers lads