It's feasible at lower levels but I've found post 20 that I've had to do all the subquests that pop up wherever the main story takes me as well as some Fates and dungeons to keep levelling on my main class. Haven't used any leves or guildhests though.

If you continue the main story far enough you'll be able to get a mount. These are very helpful in FATE hopping and can be used in your lower level classes.