Kind of hard to say. You watch or read what you enjoy. What that is is totally dependent on you yourself. I can say that you should have an understanding of the following:
DeathNote
FullMetal Alchemist
Naruto
D.Gray-Man
Meloncholy of Haruhi Suzimaya
Sailor Moon
Kingdom Hearts
Final Fantasy
Ouran High School Host Club
Pokemon
Bleach
Dragonball & Dragonball Z
One Piece
These are the main shows you will see being portrayed in cosplay (If you know of others please feel free to post them)
Other shows that are common are:
Lucky Star
Kanon
Clannad
Azumanga Daiho
Gurran Laggan
Code Geass
Fruits Basket
Any Studio Ghibli movie
InuYasha
Ruroni Kenshin (Samurai X)
Carcaptor Sakura
Trigun
Hellsing
Gundam (all versions)
Macross (ditto)
Chobits
Shugo Chara
Ghost in the Shell SAC
Cowboy Bebop
etc, etc, etc....
Believe me. With such an open request,
YOU WILL BE FLOODED WITH OPTIONS!Hope this gives you a start. To find out more about each of these go to
Wikipedia,
AniDB, or
ANN. I don't have time to link them all for you. My spelling may not be correct either, but it should get you close.
Happy browsing.