It's a bit overwhelming at first.
If you're going to use webpack, you can drop gulp.
Mix is basically a configuration wrapper for webpack.
I wouldn't reach for vuex until you feel the need for it, which probably wouldn't be for awhile. So place that on last priority.
I would start off with this series to learn the basics of Vue:
https://laracasts.com/series/learn-vue-2-step-by-step
Then you can graduate to the series that focuses on SPA:
https://laracasts.com/series/laravel-vue-and-spas
For Webpack & Mix:
https://laracasts.com/series/webpack-for-everyone
https://laracasts.com/series/learn-laravel-mix
I would worry too much about the 2 series above until you want to dive into those in more detail. The "Learning Vue2 Step by Step" covers the basics of webpack/mix enough to get you started.