Hey, and welcome to FFXIV!

In FFXIV leveling your first job is done mainly by following the main story quests including instanced content. It is not possible to skip main story quests (without a skip potion you'd have to buy separately) and all the instances are level capped, so you can't outlevel them. I've recently tried WoW so I know what you're talking about, and you don't have to worry about that happening here! Extra exp may help you skip some additional sidequests, which you can then do later on the second job you're leveling (all quests are only available once per character, no matter how many jobs you level).