A few notes:
IIRC, HP absorb doesn't absorb the amount of dmg done, but 1/10 of the amount of damage done, and MP absorb is 1/100 of the dmg done.
Read about "Materia Chains" sometime (maybe there's a different name for it now). Something some people never realize is that if you link up the same "spell" (doesn't even need to be the exact same materia) multiple times, it has ALL the effects. For example if you build up 4 "Lightning" materia, and have them all linked to something, if you cast a lightning spell that's in ALL of them, ALL of the linked effects occur. An example of such is if you had seperate lightnings attached to: HP absorb, MP absorb, Quadra Magic, and Magic Counter (or whatever it's called). Then every time you cast a lightning spell, it would happen 4 times, absorb HP AND MP, and every time you got attacked it would counterattack with that effect, again doing ALL the linked effects. This also works with the "Master Materia", so you need less of a type of materia. I often paired my masters up with HP absorb or Quadra Magic, so basically ALL of my magic was quadra, then anything I wanted to enhance "even more" I linked up seperately. The master made the normal materia orb "useless", but it was useful for the linked-in effect.
And Zeality, make sure you read the way to get Bahamut Zero. I missed it completely on my first time through (I failed the Rocket Town event), so make sure you don't miss it, though if you have a guide I'm sure that'll be no problem.
Also IIRC, the materia you can ONLY get if you have chocobos of the right color are: Mime (command), Quadra Magic (linked), HP<->MP (Purple, and useless), and Knights of the Round (summon, and trivializes all encounters EXCEPT the Weapons).