Best source of Japanese Manga that I can put into Maguro?

I'm looking to get into reading Manga in Japanse, but I want to be able to do it digitally so I can use maguro+yomitan.

I'm trying to find a good resource of where I can buy/download the original Japanese Manga, but I'm not finding a good single resource that has all I'm looking for.

Does anyone have a suggestion on where I can source my Manga downloads?