Basically there is no point in doing leve quests to far bellow your current class / job level as you'll get quite large deduction on the rewards (both XPs as well as Gills) plus you'll waste your leve quest allowances on those as well however you can re-do those as many times as you want with alternative classes / jobs (allowances permited indeed) so as you've suggested skipping those is wise decission. Rather use the allowance on higher leves in another area with your main class or join fates and re-do dungeons / duty finder quests a few times (there at least you'll not be limited by how many time you can run those and if you meet some newcommers in the dungeons and / or not die you'll gain bonus as well).