I got mine a few weeks ago and love it. I recommend you check Retro Game Corp's YouTube channel. These machines have a learning curve and there are as many opinions as users regarding what to do or tweak.
I did the following steps: 1. Installed ArkOS. 2. Downloaded ROMs (there is a Reddit thread called "A curated and scraped ROM collection - 2.0 Reupload"; downloaded and selected the ones I wanted). 3. Played with the scrapper, theme master, etc. to adjust preferences. 4. Tried different emulator settings when a game was not working well (very useful with N64 games).
I just finished Ocarina of Time and I'm playing Metal Gear Solid and it has been a blast! Hope you enjoy your experience.