Experience is easy to get in this game. It's not worth starting fresh for the experience points. For your main battle class, level is not usually what gates you from content. The main story quests are what gate you. A lot of people exceed the level of their main story quest without any special buffs. If you are behind the level of a quest you can just open duty finder and queue for a duty roulette and it will solve the problem quickly. I recommend you focus on the main story quest if you don't want to be gated from content.

Crafters and gatherers are regarded as easy to level and one of the popular ways to do it is in the Firmament, which you can unlock after getting past patch 3.3 story quests which are after the Heavensward expansion. You can also use leves and beast tribes. Their experience gain has been buffed a number of times.

If you want to experience the main story quests from scratch, you can do it on the same character by unlocking New Game+ outside of The Waking Sands in Vesper Bay in Western Thanalan.