I finally got my RDM to level 24

It took forever. FOREVER I say. I'm getting closer and closer to my BST.
I realize this is an older thread as well and I know people will say you should be leveling redmage and not have any trouble getting a party.
However, may I suggest the blackmage soloing areas. For a redmage...lol, even a white mage...there is just no reason to not be able to easily solo up to level 37 in a short amount of time. White mage is quite a bit more difficult, but I have seen it done.
Red mage, Scholar and Black mage though...no debate. If you are no tarutaru, then use + MP items and/or MP recovery food + MP recovery gear. Use swap out gear for between adding +INT and then switching to +MP recovery gear in the applicable slots.