DC Universe (soon to be DC Universe Infinite) seems to be the best source for DC material in digital form. Comixology also works but is more expensive in the long run. Those are the only two legal options I know, really, and it’s against the guidelines to suggest an illegal website for such a thing.
As for recommendations on Teen Titans, I’ve read every Titans title ever made, so I have you covered there. Just let me know in one way or another what you’re hoping for most from Titans recommendations. Maybe you’re wanting a good starting point for understanding the larger lore. Maybe you’re just wanting good stories and don’t care where in the publication timeline they fall. Maybe you have certain characters you like and you’d like to read titles that include them on the roster. Whatever works.
I have read a few Doom Patrol titles, too, and I understand a decent amount about the ones I haven’t read. So you could ask about DP as well, although I would welcome a more knowledgeable user to come in as well on that point.
