from what I've seen in the brief time I've been lvl 50 on my DRG... all the gear you use doesn't even have slots for materia. The AF gear doesnt, and neither does the AF+1 gear which I think is considered the best gear in the game currently... not too sure about Darklight, dont remember. Which has left me wondering what the whole point of it all is if the best gear in the game doesnt even allow you to use it.
Currently iLvl 70 HQ crafted gear = Darklight/Mog/Garuda/Titan even without Materia. For example, Heavy Darksteel body is almost exactly the same as Heavy Darklight body with zero Materia, and it has 4 safe Materia slots. Basically if you don't want to grind for DL or you want shinier stuff than DL without going to Bahamut Coil, then it's HQ crafted gears + Materia. You can also *dye* them.
iLvl 90 (Allaghan) and AF 2 are non-meldable and highest tier.