Some of my mates play limit and makes a greater profit than I do at the NL-tables (higher stakes than I play though). I think it's more about what suits you. I got tired of the lotteryfactor when there were 10 peoples in every pot. On the other hand you can win some big multiway pots that way. And if you play higher limits it aint all like that. But I guess if you are new to the game you will struggle on the 0,5/1 tables. I would consider trying out pot limit. You get rid of the maniacs capping every pot pre-flop and you can still get a lot of chips in the pot and punish drawers if the flop/turn suits you. I played two tables yesterday one $50 PL and one $50 NL and the pot limit table was what saved my day. The game was much softer there and since I didn't have the greatest run of cards on the NL table I ended up a $100 down there ( got KK broken by Ax, AK by KQ etc. very frustrating). Luckily for me I won about $150 on the PL table. This might have been a coincidence but I felt the standard of the players at the NL table were a bit higher as well. And besides that some of the best players thinks a good player has a greater edge in PL than in NL. Anyway just try it out and see what suits you. Most people are having a hard time the first months. About moving to a higher limit. I think you should do this before switching to HIGHER limits (nothing to do with fixed/NL/PL):
A) Build an appropriate bankroll
B) Make sure you can beat the limit you are allready on. That can't be done in less than at least 300 hours because of the "luckfactor" in the game. If you decide you are a winning player at that limit then move up but be prepared to move down again if you get your ass kicked. These are advices given to me and others by better players and I think they are accurate.
What ever way you choose:
Good Luck and Have Fun!