I'm leveling all DoH classes at once and gather all my mats; inventory has always been a toughie. One thing I do to help is assign item types to each retainer. In my case, weapons/gear are on retainer 1, ltw/wvr on 2, alc/cul on 3 (some overflow onto other retainers), and arm/bsm on 4. Random stuff like atma, materia, fish, and dye go onto different retainers depending on how much space each has. I do try to clean things out once in a while and sell off what I can.
