Don't worry your doing great (including Pcpartpicker list is much better then a lot of newbies).
That's a pretty solid build. I would say unless your having any specific issues (really long load times, heat issues, et cetera) the most obvious upgrade would be a cpu upgrade (GPUs are flat out too expensive right now especially because the one you have is pretty decent).
That said, what kind of monitor are you using. An upgrade to a 1440p 144hz monitor may be a much better investment then any other kind right now. If your monitor is 1080p 60hz then it's definetely your biggest weakpoint.