Here you'll find the name of each magic materia, the spell(s) it casts, and where you can buy or find it.
BARRIER-Barrier/MBarrier/Reflect/Wall-Buy Rocket Town
CONTAIN-Freeze/Break/Tornado/Flare-Feed the chocobo in Mideel a sylkis green and scratch it behind its ear
DESTRUCT-DeBarrier/DeSpell/Death-Buy Mideel
EARTH-Quake 1,2,3-Buy Kalm
EXIT-Escape/Remove-Buy Rocket Town
FIRE-Fire 1,2,3-Buy Costa del Sol,Mideel
FULL CURE-Full Cure-Cosmo Canyon in disc 2/3 go through the previously locked door in it'll be in the next room
GRAVITY-Demi 1,2,3-Jenova Life
HEAL-Poisona/Ensuna/Resist-Buy Gongaga, Junon
ICE-Ice 1,2,3-Buy Wall Market, Costa del Sol
LIGHTNING-Lightning 1,2,3-Same as above
METEO-Comet 1,2-Bone Village
MYSTIFY-Confu/Beserk-Buy Cosmo Canyon
POISON-Bio 1,2,3-Buy Kalm, Find Shinra HQ
RECOVER-Cure 1,2,Regen,3-Find Reactor#1, Buy Wall Market, Mideel
REVIVE-Life 1,2-Junon
SEAL-Sleep/Silence-Junon
SHIELD-Shield-Find Northern Crater where the Magic Pots are
TIME-Haste/Slow/Stop-Buy Gongaga, Rocket Town
TRANSFORM-Mini/Toad-Find N. Corel, Buy Cosmo Canyon, Gongaga
ULTIMA-Ultima-Save N. Corel others wise pay the boy 50,000 gil