[Harv72b]

It is much easier to profit on the lower limit games. In fact, there are only two reasons I can think of to ever move up:

1) To challenge yourself/improve your own poker skills.
2) To maximize your winnings in pure dollar form, rather than BB/hr. I.E., netting 1 BB/hr on 5/10 will make you more money than winning 5 BB/hr on .50/1.

As far as where to start, it depends entirely on the individual. The learning curve will be much steeper if you start at a relatively high limit, but if you have the capacity to keep up with that pace & the bankroll to absorb the inevitable losses as you learn, then it would make more sense to start at a higher limit (probably 1-2 steps below the 300 BB rule--if your BR was $30k, starting on 20/40 rather than 50/100). But if you get frustrated easily and/or cannot afford to bleed off a significant portion of your bankroll, you're better off starting at the lowest limit you can tolerate and working your way up from there.