Start writing and keep writing. There will be many pitfalls along the way and grammatical nuances to overcome but if you so desire, you will achieve it.
As for reading material I recommend intermediate level books usually targeted for young kids. Why?
In most cases, learning the fundamentals of how something works can go a long way.
Riding a bicycle may be simple now but as kids we had to learn it at some point.
Professional BMX freestylers started out the same way but elevated their skills and dexterity by practicing further than what you and I are accustomed to.
Learn the different meanings of what one word may posess.
For instance, 'hold' has many different usages.
I held your arms
I held up my bargain now its your turn!
Hold on, Im on the phone.
The prisoner is in a holding cell.
Please put that call on hold.
I will hold you to your promise.
Make sure you have a firm hold on that rope.
Relax and try to hold in your anger.
Men! Do not surrender, hold down the fort!
As you can see, this one little word can branch out into different meanings just by context and prepositional phrases alone.
Speaking of meanings make sure that you try to use the correct word for a given idea, situation, sentence, etc.
I got a signal from outer space.
I received a signal from outer space. (yes)
The car was going at 90 mph on a rainy day. Suddenly the car started turning left and right and crashed a tree.
The driver was going 90 mph on a wet slippery road when suddenly he lost control of the vehicle, swerving left and right and finally crashing head-on with a tree.
Keep ideas simple:
I'm fatigued. It has truthfully been almost an hour since I have had anything to consume.
I'm tired. Its been an hour since I've eaten.
Keep medical terms with medical context just like keep legal terms with legal documents. In other words, if you are writing an article about Biology you wouldnt use terms you otherwise would use in everyday speech.
Some of these viruses stick to healthy cells.
Some of these viruses attach to healthy cells.
These veins send blood througout the body.
These veins pump blood throughout the body.