Turning 1 Faerie Ring into a Mystic Symbol is one I do every time. You get 2 Faerie Rings but only 1 Mystic Symbol and I find the latter a must for any spellcaster.
After that I guess the best use for runes bottles is herbs. Getting 999 TP on either Keele or Meredy to be able to do Maxwell's Extensions, otherwise buffing Reid's stats since he get a few solo battles.
Grand Marshal/Gladiator Priest, Lightplol. PvE gladiator holy paladin, Lightp.