When you are first starting the game of table tennis, it is very important that you know the correct strokes and can read spin. For people just starting, I would suggest that you mostly focus on learning your strokes. Because in a game, you can sometimes lose focus on your strokes, and concentrate more on just getting the ball back on the table. If you just work on getting the ball back, your strokes will become sloppy. And once they become sloppy, it is VERY hard to fix them. So I would suggest mainly technical training at first. But make sure you know how the strokes should be, and once you learn them, practice them over, and over again. A good tool for practicing is the Newgy Robo-Pong table tennis robot. This will allow you to work on a shot for a long period of time.
Now, even though you should do a lot of technical practice at first, that doesn’t mean you shouldn’t play matches at all. Playing some matches is good. A good ratio to go by is, for every hour of matches you play, you should train about five hours.
Once your strokes become more natural and consistent, you can slow down with the technical training. But that doesn’t mean you should never train again. Just make sure you keep your strokes correct.
Now if you have been playing for a long time, it doesn’t mean it is too late for you. You can still begin to practice a lot on your strokes, and your game will still improve.