Money enters the official loop in one line: earn money from your OP pets. "OP" here is the description's own word for those pets. No other income source is named. Eggs, backflips, and the treadmill are not described as cash generators.
The path that creates the income
- Backflip to a new biome.
- Steal an egg from its guardian.
- Hatch it into a pet. Some pets are mutated.
- The pet is what the list says earns money.
The description stops there. It does not say whether a rarer egg, a mutated pet, or a larger collection pays more. It does not give a number per pet or per second. Any "best earner" ranking that quotes a rate is not backed by this text.
Cash on the store
The game store sells a pass named x2 Cash. The How to Play line says money. The two words may be one balance, but the description never defines that. The pass is a multiplier for sale. It is not proof of a second currency, and it is not required to earn the pet income the list already names.
Spending
No price in the official paragraph is assigned to anything. The systems that follow the money line are treadmill Speed training and treadmill and base upgrades. The text never says those menus spend money. Open them in game before you assume an order of purchases.
There is no fact-based "buy this first" list. The useful order is the loop itself: reach an area, bring an egg home if your session requires it, hatch, then read the upgrade screen you actually see.
Collection strength is a separate claim in the longer recorded description: hatch and grow powerful animals, and build your collection to become stronger. That wording does not convert strength into a money formula either.