I forgot to mention, as some others have, pen and paper RPGs and board games are a blast. I recently started playing those and being 32, wish I had started when I was a teenager. If you like RPG PC games you would enjoy the pen and paper variety. I always thought they were too nerdy, even for me but now I can't get enough. You basically roll dice to see whether or not you hit and how much damage, in addition to other skills. Your rolls are basically what the program does behind the scenes.

I recently started playing League of Legends. While you can use keyboard shortcuts, I generally play with just a mouse. It's free or you can spend some money to purchase points in which to unlock Champions. There are free Champions available each week to use and when you play you earn points which can be used to unlock more. There are the old (and new) point-and-click adventure games which I've always been fond of. As some people have suggested, Civilization is a good game which also plays well with just the mouse. Magic the Gathering Online, Carte, and Shadow Era are pretty good card games which are played with a mouse. They are collectable games and Carte and Shadow Era don't require much investment. Decks and boosters in Shadow Era are only $1 a piece and furthermore you earn points through winning against AI or online competitive games which can be used to purchase boosters and cards. Also if you have a device with a touch screen some of the Android or iOS games are pretty entertaining. The Shadow Era game I mentioned above can also be playing on either OS so you can play on the go. I play a number of tower defense games on my phone which are also available on PC and just require a mouse as well. Also available are gaming mice which have tons of programmable buttons which can be mapped to play FPS games, although it may be a challenge playing online against other players but not impossible. If you are able to use a finger or device to press the WSAD keys it would be even easier. Hope you can find some games you enjoy.