World of Tanks

This is quite straight-forward. All Tier 1 tanks are light tanks, and a lot of Tier 2 tanks are Light tanks as well! Light tanks have a solid diamond by their Tier number.
Just start a game with your light tank, if you get destroyed you can just go straight to your garage and pick another ready light tank and play another match! It will take some time to get the last Light tank matches played achievement but don't spend too much time watching games finish after you're out and it should go faster:

This achievement is pretty easy. It just takes a while to play the 50 games. It doesn't matter if you win or lose.

You can unlock a Light Tank at tier 1 on every nation tech tree. A Light Tank has a symbol of a Diamond.

You can check your progress by going onto the stats page while in the garage for each Light Tank you play. Or since you're on the Xbox one version you can check the percentage on the achievement when you snap.

This doesn't have to be done all in one Light Tank.