Focus on PLL execution and learning OLLs.
If you're sitting in a place without a computer access, try not to scramble the cube and practice solves so much when you have such a long way to go with PLLs. Focus on PLLs for a while FIRST. Maybe, do each algorithm like...50-100 times before even touching the timer. Try to perfect the algorithm. If you have computer access at the time, then focusing on memorizing the OLLs. There's really no reason to wait so long on them when you could just get them out of the way. You could learn like, half of them within a week, then the other half next week, if you have the time, or if you're that fast at memorizing. Either way, I'd say just get it out of the way. And you have no reason to try and limit your memorization capabilities. You'd be surprised what your brain can do if you try hard enough.
I'm no expert, but here's my two cents on what to do after all is said and done:
Once you're sub-20, it would be good for you to always be looking for new algorithms to learn. Once you can't find any algorithms, find something else to learn. Always be learning something. I'm just starting to learn F2LL (Winter Variation). It's gotten me a few extra sub-10 solves where I otherwise wouldn't have gotten them. Once I've learned that, I'm going to learn OLLCP, and then some COLL, and maybe some CMLL that could be used on both Roux and Waterman solves. In the meantime, outside of algorithms, I'll also be practicing EOLine and EOCross for OH-solving. Still haven't perfected it. (For some reason, I keep misidentifying bad edges...) Because of this, I'll probably end up learning some ZZ too. I bet learning some phasing might help me with my F2L too. Once I've conquered all this, I'll hunt for more algorithms, Maybe I'll start ZB-method too. That should be fun. Doesn't really matter what it is. All that matters is that I'm learning something. Just learn as much as you can as fast as you can, and you should be fine.
But, of course, don't neglect look-ahead. Your main focus should almost always be cross and look-ahead (mainly look-ahead). Learning algorithms is just a given. You should always be doing that on the side, but the main thing that will get you those awesome times is cross and look ahead. If you're cubing and have nothing better to do, then work on cross and look ahead.
Also, try to structure your practice time. Make a schedule or something. Structured practice time might do you some good. At least make a sort of general structure. You could maybe separate it into algorithm-learning and execution, cross, F2L, and full solves. "First, I'll memorize these 10 or so algorithms, then I'll practice my cross for 30 minutes, then I'll practice F2L look-ahead for 30 minutes, then I'll practice my such-and-such for so-and-so minutes, and then I'll work on blah blah blah." You tweak it to suit your needs.
Another tip: Always stay relaxed when solving. A good way to do this is to move the cube at a speed just a HAIR below normal speed. Your eyes should have an somewhat easier time keeping up that way, and your hands will be able to relax a bit more easily.
Hope that helps.
