I would start a small hobby project in whatever language and platform you'd like to work with, pick something you enjoy so that you keep building it for a while

I would start a small hobby project in whatever language and platform you'd like to work with, pick something you enjoy so that you keep building it for a while. That's real experience that will expose you to many issues you wouldn't have known about otherwise, and will give you lots of platform-specific things to talk about in addition to your previous experience.