I've got a few questions related to this:
- Can you put Materia Slots in gear?
- Does AF+1/Relic+1 come with Materia Slots?
- Does Allagan have a chance to be dropped with Materia Slots?
- Could the maximum number of Materia Slots be different for both pieces of gear?

Also, with regards to classes and jobs, which gears are class-restricted and which ones job-restricted?