The most common suggestion I read when people ask “how to work as a game designer?” is: participate in game jams.
In my humble opinion, this suggestion is incomplete. In fact, game jams are a cool event where you are forced to make decisions quickly and to join the ideas of all the team in something you really want to show at the end. The time you have usually is very low, so that you feel you are really pushing your boundaries. As experience is great and you can also make meaningful connections.
BUT, game jams lack a very important element for game designers: Players. The result of your hard work will probably be shared with other game developers and also the final result is often voted by devs. Nothing to do with the real struggle of game design: understanding behaviors and needs of the people that are willing to play your game.
Once your game jam weekend is over, maybe you achieved great results. End a complete experience is a great result, arriving in the first 10 positions is. The first 3 is a great result. The 1st position is awesome! And then what?
Then often you speak with your colleagues, you polish what you did and you just publish it.
Try, instead, let common people play your game. Start with your family, especially the kids if you are lucky to have them around. Look for proof that your game doesn’t work! Do not look to confirm that you had a great idea. You have to put your concept in crisis if you want to really pass to the next step: publish something meaningful.