Cloud Farm becomes available at level 36.

How to register a Cloud Farm item in the Gallery?
Step 1: Reach Cloud Farm level 2.
Step 2: Tap the Gallery icon in the bottom right corner.
Step 3: Tap the item you want to register.

How to get more Cloud Coins?
1) Complete Cloud Farm tasks.
2) Complete as many Adventurer's Bazaar orders as possible.
3) Load as many boxes in the Adventurer's Zeppelin as you can.
4) Sell Cloud Farm products from the Barn.