The best way to learn is to start photographing more — both for the basics and for more advanced photography.
This is a particularly good answer to the "should I buy more lenses for the KS-2" question, because a lot of the answer depends on whether you find yourself really enjoying using it.
But, of course, film requires a greater time and patience commitment, and the per-shot costs (along with delay until you see results, and lack of automatically-recorded metadata) make experimenting a different process. That difference is not necessarily bad — in fact, arguably it's a great approach to serious learning — but it's not for everyone.
So, if you're going to spend some with film and aren't comfortable with the very basics, it's not a bad idea to make sure you understand what's happening with the basics of exposure — aperture, ISO, and shutter speed. There's dozens of books and web sites, and any of them can teach you about this, if you don't forget the key point, which is: the relationship is actually quite straightforward, so if you get confused, your teaching resource is probably broken in some way. (No problem: ditch that book or web site and pick up another.)
Beyond that, I find it nice to learn and mentally process while I'm working, a little bit at a time. Make sure to make at least one picture every day, and make sure every week to look at the pictures you've taken. (If you end up taking lots, take that time to weed out the very best.) And, at the same time, find a good book, and read it just a page or two a day. (Michael Freeman's books are well-suited for this; I just finished Perfect Exposure in this way, and am about to start on The Photographer's Mind.)
So basically: don't let being worried about lack of knowledge keep you from getting started. Mistakes are great to learn from, and if you're busy researching, you can't make any.