the One Piece manga.
you can buy the volumes or read them online at onemanga.com (but this is technically illegal)
buying has many advantages, but if your short on cash go with online. the thing the scans can be rarely low quality, and the quality of the translations varries and can cause confusion.
That being said, last time i checked its the number 1 manga in Japan, and number 3rd in the US.
I highly recommend it.
