I don't know much but I'd say the Empire is probably one of the more strait forward armies to use considering the amount of flexibility with them.
If I had the money and time I'd have either a Tomb Kings army or a Lizardman army. The Skaven are a fun bunch(kinda like a different version of orks I suppose) with their warp cannons blowing themselves and their crews up and misfiring into their own ranks(doh!). And I tend to think the High Elves as an elitist force considering(from what I remember anyways) that their armies on the TT were usually smaller than most but could definitely hold their own.