Here are some things to practice on your own. Just 5 minutes a day can make a big difference.
Practice the spike approach
Serve to a wall
Set to a wall
Pass to a wall
I'm left handed, so your steps are opposite. I go right-left-right. You go left-right-left.
For the approach, first practice the last 2 steps.
Start on the left foot, then take a big step to the right then quickly left... plant both feet and jump. As you take the big step remember to bring the arms back.
Add in another step. Start on the right foot, step to the left... take a big right then left... plant both feet and jump. And don't forget to swing the arms back.
Start deeper in the court and take steps to get to the start position. Then practice the 3 step approach.
Pick a spot on the wall to aim for. Serve just as you would normally serve. Focus on a consistent toss, armswing, and contact.
Practice setting the ball to a partner or a wall.
In this video, I show how to use a heavy ball to help get stronger. This will also help improve coordination.
If you're interested in buying a medicine ball, they should have them at Dicks Sporting Goods. I would get the 4 pound ball. Get one that bounces like the one in the video. And you could use a basketball or volleyball instead of the medicine ball for these drills.
You don't have to do everything in the videos, just do what you have time for. Just 5 minutes a day will make a difference.
Focus on continuous passing to the wall. Set a goal of 5 passes in a row. Stay low and keep the knees bent the entire time. After you can do 5 in a row, make a goal for 10 in a row. Work up to eventually pass to the wall continuously for a minute without losing control.