I think loading your RM with an exclusive type of magic is very wasteful. Every level of magic has spells you will never use, and it's not too hard at all to reach a good balance. I always give my RM the following spells:

LV1: Cure, Fire, Lit
LV2: Ice, Invis, ALit
LV3: Fire2, Lit2, Cure2
LV4: Ice2, Fast, Pure
LV5: Cure3, Fire3, Life
LV6: Exit, Bolt3, Invs2
LV7: Ice3, Arub