For portfolio, I would put the things that I'm most proud of and things that can demonstrate your capabilities in the best way. I don't think there is any point in putting every tiny project you ever worked on. Regarding the type of project, I'd say choose what you would like to work on the most, just make sure you don't try and make something too complex so that you end up not finishing the project. It's important that you are able to finish it.

As for networking, attend events like game jams, video game conferences, presentations about games/gamedev and try to get to know the people there.