For starting out, HeadsUp would be just about the worst way to go.
I think a decent game to start out with are the 9plyr. SNG's, although I wouldn't go so far as to say that they are an easy way to build a bankroll (depends on what site you're playing on, some are still very soft but the bigger sites have some decent players even in the micros).
For a beginner getting started, playing NLHE online, I would personally suggest:
2nl FullRing - Buy in for 100bb's ($2) and get some experience at that level.
SNG (9plyr.) 0.70 SNG Satellite (basically a 9plyr sng but top 3 win the same, $2.20).. or $1 or $2 sng
SNG (45plyr) $1 buyin
MTT - some $1 or $2 MTT's.. maybe the DailyDollar 'rebuy' & some other micro rebuys.
Play a handful of each & find what you think you like the most, then put in a bit of time learning that one format... then try to stick to just that 'one' until you can get fairly decent at it before moving around to different games.