This is my first post on this website; I was looking for some advice and found this forum. I started playing Go about 9 months ago, and didn't really find myself improving much. It took like 7 months to become 17k. But, the last 2 months I've really been studying as much as I can on Sensei's library and am now at 8k on KGS. The problem is, I don't really know what I should be studying from here. I've learned all the common "good" and "bad" shapes, studied so many life and death problems, different openings, joseki, etc. What should I really be focusing on as single-digit kyu?

As a SDK, you could be very good at some facets of the game and not so good at others, so it is hard to say. ( As opposed to a 20K who is certain to be bad at everything, or a mid-dan who must be at least competent at everything )
Post a game or two in the 'game analysis' sub-forum, and we'll tell you where you need to improve.

BTW, welcome to L19.

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Help make L19 more organized. Make an index: https://lifein19x19.com/viewtopic.php?f=14&t=5207

Thank you! I didn't know about that outlet. I'll save the .sgf of my next two games on KGS for advice.

No need, you can find them here: http://www.gokgs.com/gameArchives.jsp?user=Paradoxgo