Depends on how fast you want to go. Powerleveling yourself will cost lots of gil unless you gather your own materials. Even then you'll want everything HQ to make leveling faster.

You'll want to do your leve quests and do all HQ turn ins for double exp, as well as daily turn ins at your GC. The faster you go, the more expensive it can be, but if you have a lot of gil, then it won't matter. You'll run into a wall though once you run out of leves however.