You can earn gems in the game by:
- Serving customers and getting tips
- Leveling up in the game
- Achieving your next chef rank in the achievements
You can earn gold coins from:
- Serving your clients the dishes you have made - you can see in the Academy how much each dish sells for once you have unlocked the Chef.
- Selling items on the Social Market to other players
- Selling items to the salesman Tex
- Completing an event in the Chill out area
- For free in the Local wholesale deliveries which you obtain every 6 hours
I hope this helps.