You should just use platinum armors and spirits to level them past 50 or so. The second set of tables here show the optimum level/xp remaining for the units to avoid wasting XP when using the platinum armors. Don't worry about spending all your SC on the daily, you'll get the plat armors readily enough if you just farm it each week (also when events start up again you should be able to get some from those). If you can, try to get to Base Scramble II to farm, as it gives better XP per charisma.
Claudia is much better.