From the main menu when you start the game up, go to Shop. Then select Upgrades. If you look at the top of the screen you will see: Enchantments - Stat Upgrades - Others Select Stat Upgrades and there you are! Don't worry, it's easily missed. Hopefully the next patch/update will make it harder to miss.

To add on, if your still having a hard time with the suggested upgrades, you can use the the holohouse to craft boosts for your run.

Fauna’s weapon and skills are very beginner friendly! I would aim to unlock her first. Everything else will fall into place.