I’d say learn to spin your groundstrokes first. Starting with topspin. (Angle racket with top slightly further forward, swing over the ball) You can’t get any type of power going until you can keep the ball down. Start at a speed you can control decently well every time and pick small targets. Keep going a little harder until you’re at a satisfactory level of speed and you can keep it in/in the general direction you want to go.
Then work on your serve, like the groundstrokes only start out as fast as you can keep it in the box every time. Add speed gradually. I found that a bucket of ~50 balls and hitting them all in one sitting is the best way to try little things, kind of like the driving range.
Finally, work on your volleying and court positioning, for this one you’ll need a partner to hit you balls just over the net and hustle you around the court. One of the easiest things to do decently, but one of the hardest to do well.
You have to build into hitting power shots in tennis, starting with a wild shot and trying to control it is much harder than starting with a slow,accurate one and building speed. Plus, in the meantime, a well-placed shot can win you the majority of points.