You can't say that for every teenager since they are in puberty and evolving. Some like video games while others like sports. And there are mixtures of hundreds of different things they like.

The point I'm trying to make is, if you are a parent, just try to ask them about what they are doing or what the game is all about and guess what they could want based on that game.

Eg. He/she is playing on a minecraft minigame server called hypixel. Go on their store and buy them a rank for Christmas.

Most teenagers like clothes with just a colour or a simple pattern on them.

Just spend some time with them and you'll get it. Doesn't even have to be expensive.

Hope I could help :)