[@KatherinWinter] 
Primarily research in Holder magic sense that's where all the magic item users are, not to mention specific on just magic items in general, so basically I'm having to read pretty much 99% of everything in this forum

http://fairytail.wikia.com/wiki/Category:Holder_Magic?display=exhibition&sort=mostvisited 

to learn everything about holder magic and their specific magic items, though there will probably be some magic item information that just isn't easily found. Though not everything on the forum is actual holder magic which sucks lol. so that makes it bit harder there. Also he can't do anything in regards to celestial spirit keys, they are uncreatable. so there wont be any insane cheatings there.