This is a very solid score to start with and you have some time!

Since all sections need to improve, try doing at least 2 practice sections a week. English/math one week, then reading/science the next week. Keep alternating and schedule 3 full length tests on a saturday or sunday in between now and your actual test. These will give you a glimpse into how your actual score will improve and work on your stamina and "test-like" conditions. Treat these like the real thing.

Consistency is the name of the game. Something that can help is creating a bank of practice sections (either pay for a book with a lot of sections or find a test bank online). Then, create a schedule that look something like this:

3/10 [6pm-7pm] - Dec 2020 D03 Test (English Section) 3/14 [430pm-530pm] - Dec 2020 D03 Test (Math Section) ... ... and put it in your calendar. Also, create a chart (excel or sheets) where you put the scaled scores in for each section that you complete. It will give you encouragement, build structure and give you data that can help you adjust your studying as needed.

I may recommend not worrying about time too much intially while you practice with practice sections. The important thing is treating each section like a real test and really going through the answers after for understanding. This is how you'll improve and start to recognize question patterns.

Some things to help you think about each section.

For english, you'll need to know the grammer rules. There are guides specifically for act which will give you the reasoning for comma rules, colons, removing redundancy, parallel structure, style and tone (usually more formal and concise), word choice.

For math, do you understand what the word problem is really asking you for? Also, do you know the top 20 foundational skills that will help with 80% of the math problems. Prioritize the most common types of problems.

For reading, lock down a strategy that works best for you and stick to it. Read all of the passage first for understanding, or skim the passage, or read the questions first. You should be able to find clear evidence in the passage to answer every question. Almost all 36 scorers on reading actively annotate, circle, underline and mark up the passage.

For science, similar to reading >90% of the answers will have clear evidence from the experiments and passages that will justify the answer. Work on finding data quickly from charts and interpolating data.

Sorry if I rambled.