>>83066012If you're looking just for Adam Warren's work on the main Gen13 series, part of it's been been collected in two trade paperbacks: Gen13: Superhuman Like You (collects issues #60–#65), and Gen13: Meanwhile (collects issues #43–#44 and #66–#70). The final storyarc, issues #71–#77, have never been collected, though, so you'll have to get the floppies individually.
There's also his work on issues #8–#10 of the Gen13: Bootleg spin-off series, which has been collected in the Gen13 Bootleg: Grunge the Movie trade paperback. And then there's the Gen13: Magical Drama Queen Roxy 3-part miniseries (he didn't draw this one, though, just wrote it, and it's one of the weaker portions of his Gen13 work, and I'd recommend it only if you're going to be a completist about Warren's Gen13 work).
These are all currently out of print as far as I know, so your best bet, if you want to get the physical paperbacks/floppies, is Amazon or eBay (or I dunno, try contacting Warren on social media and see if he's got any old copies he's willing to sell to you directly... I don't know if he's ever done anything like that, but hey, it could happen, and you'd get an interesting story out of it).
If you're going the piracy route, torrents or libgen are probably the way to go.