just click stuff. Hold your left mouse button to make the cat move/train. the Battle button will allow you to compete against AI opponents, make sure your fast enough. The upgrade menu is a menu where you get better stamina, restoration and speed. Gems are a currency that allows you to boost yourself a bit (but then helps save up to get the next speed upgrade). Free gems happen every 5 minutes. When you defeat an opponent, you get an reward, depending on your opponent. There are 2 categories, Ground Things and Water Things. Click on the button that says "Ground Things" on the battle menu to switch between categories. Opponents must be unlocked before playing the next one.
c2a. i like clicker games but they are GRINDY.