Look on the tank section of the forums. There are some guides there and discussions of aggro. At your current level you will basically want to hit something with shield lob and then flash several times when the mobs are in range.
There are other responsibilities that usually fall to the tank (like marking) which you can work on when you are comfortable with the basics of holding aggro.

Currently the only advanced job for gladiator is paladin. To unlock that you will eventually need conjurer up to 15. So if you want a break from tanking for a bit, you might start leveling that. If you prefer something else over tanking, go for it. Tanking will get you almost instant access to the dungeons but in exchange you get all the stress of tanking :P