Paladin requires Conjurer lvl15 and Gladiator lvl30. Paladin shares some cross class skills with Marauder so it's only gonna help you down the road. As far as crafting goes, I'd suggest Goldsmith. It's a great way to make money and it's very easy to lvl. If you're super serious about crafting you should level ALL crafting classes to at least lvl 15 for the cross class skills.

This site is super helpful:

http://ffxiv.gamerescape.com/wiki/Paladin