One very significant porblem with Mick's advice.
If all you do is "go out there and play" without instruction and advice you will most likely injure yourself, sometime permanently.
In fact, some of the safest and most effective ways to play tennis are NOT intuitive. And some of the most intuitive ways to hit are the MOST dangerous to wrist, elbow, and shoulder health. Just watch an untrained player serve and you'll see a "surgery patient to be".
I fully agree with Mick that court time is crucial. I quit one team because most of the guys would only show up on match day and then complain about getting their clocks cleaned. They literally wouldn't come to practice with a teaching pro or just hit casually. Meanwhile I was busting my butt many nights and even lunchtime to improve my serve and arranging practice sessions. Truly annoying.
There's no substitute for court time and match time but to make it efficient, safe, and beneficial it's best done with some thought and guidance by those with experience.