baseball is unique in that there are many things you can do by yourself in fact that's 1 of the most common questions what can I do to improve outside practice when I'm by myself or at home.  This is 1 of the best things I've seen and was suggested to any player that wants to work on his own  and improve his throwing, pitching, fielding, even his foot movement.  take a look at it and see what you think and if it doesn't give you  some good ideas and some possible drill work.

Find the side of the building, get a tennis ball, and a piece of chalk. Now go draw a person on the side of that building (it can be just a stick man). Take a tennis ball and throw it to the man on the wall what will happen of course is that tennis ball will bounce back to you and you will get good practice at fielding the ball along with throwing. And if you pay attention you will get better and better at hitting the stick man. It just takes a lot of pitches before you get really good but if you'll stay after you  will be able to play catch and not have to chase the ball all the time but you'll have to do some of it on your own and what I suggest will work. By doing this and having fun you will develop the most important infancy skills, fielding, throwing with accuracy, and just having a good time learning/