I have never read the Ginga mangas for many reasons. One, I don't know where to buy them. Actually I do, but not in english. I found one in english but it was like $100, USED. And three, I need a website I can trust to buy them from. Forget Ebay. Sometimes, people just steal your money.
So anywho, I've only read the manga online. Onemanga.com closed down so they can no longer put up mangas. Mangareader.net is what I use to read GDW. It's not that bad, but the pages will get stuck sometimes. Google the images of the manga and the website of the image may have the manga.