hee hee... you stepped into the lions' den here with your mentioning of Hanon and Czerny. I will leave the bulk of that discussion for those who love to discuss it, however I will briefly mention that there is one thought along these lines which suggests that one need not practice Hanon and Czerny to improve, but only pieces from the repertoire (along with knowing your scales). Also, along those lines, the same thought suggests that technique cannot be learned in a vacuum, but is only relevant to musical content.
I happen to agree with everything mentioned above. So, my advice to you will be along those lines.
Pick 4-5 pieces that are varying in difficulty and musical/physical requirements. One will be a "project-piece" and will either be the longest, or the most difficult out of all of them. In any event, it will take a bit longer to master than the others. Then pick one that will take about half that long, and then 1 or 2 that will take only a very short while (and once these are learned and mastered, these are replaced with other easy pieces as you go).
Practise sight-reading two ways :
1. Getting in any notes you can, in time.
2. Sight-reading out of time, only moving your hands when you are sure of where you are going, aiming for accuracey without looking.
Make a practice schedule and log your practice. Keep a practice journal to keep track of your specific progress.
Other than that, search the forum for "sight-reading" "practice" or "practise" and anything else you are interested in.
Oh yes, and there is no need to wait to start improvising. Do a search under the word "improvisation" and "Ted" and you will find some great ideas there.
Welcome to the forum

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m1469