T1-2 materia are cheap, T3 are usually fair price, and T4 is only used for stats you're pushing over 75% cap. Considering only 25% of the materia you need is actually legitimately expensive, you've got 56-some Alexandrite's worth of time to farm for them. It's a lot of money if you're not spiritbinding yourself, but if you are, I'm sure you'd make plenty of gil to buy what you didn't bind yourself. Or craft. Or do dailies. You don't need the game to hold your hand with materia if you've come this far farming mythology and atma.