These are personal experiences I have had from being a self taught artist and is written down here for you to help promote a healthy mentality of developing and strengthening your skills.
I personally recommend to start with strengthening your foundations. But it also never hurts to think of a short term goal and then taking a step back to think about how you can achieve that goal realistically.
A way to keep improving is this: with every new piece you want to create, have a look at your last one. Take note of what you liked, now take note of what you didn’t like. Of the things you didn’t like, make it your goal to improve on that with your new piece.
Keep yourself in a positive mindset and only compare your current works to your past works. Everyone has different levels of experience. What matters is your own personal improvement over time.
Learning to look at a monitor while your hand is drawing on your tablet can be a challenge. I recommend an exercise called blind contour drawing which will help strengthen hand / eye co-ordination.
When you have 20 minutes of spare time, watch this video from Neil Gaiman. This has saved me time and again as an artist and as a human being.