The early thirties are a tough time for White Mages. They give you Cure II to waste more MP and Presence of Mind to waste it faster.

If you're struggling, a good practice is to drink a hi-ether after you've spent a little MP and then again on cooldowns. You probably have enough hi-ethers from quests to sustain this until you get the rest of your abilities. Stoneskin on the tank between fights will allow you breathing room at the start, Regen will give you opportunities to sit and recover MP rather than chaining Cures, and finally Shroud makes White Mage actually work! Plus Divine Seal allows you to counter heavier damage with cheaper heals.

Combat Raise can be a real drain on your reserves and may make fights hopeless if you have to waste too much MP on it. Even so, it is better to pick up fallen damage dealers and let them learn the fight than conserve MP while they lie in the dirt. Such groups are looking at a wipe anyway, try to maximize the educational value.