Honestly, I'd save up and invest in a high quality wig. It'll be worth it, trust me.
As for which dyeing method to use, it depends on the wig's fiber type (kanakelon, hiperlon, human hair, etc.).
Finished: Armin Arlert, Mayoi Hachikuji, Tomoko Kuroki, Ultimate Madoka, fem!Masky
In progress: Kougyoku Ren, Lightning Farron
Upcoming cons: Sabakon, Youmacon, Con+Alt+Delete