Quick answer
What to do
Pick one next goal, compare the displayed cost with your current earnings, and avoid spending everything if it leaves your pets unprotected.
1. Choose the goal
Decide whether cash is for another pet, stronger base protection, or preparing a raid.
2. Compare visible values
Use the current price and income shown in game. Updates may change these values.
3. Keep a defense reserve
Do not turn every earning into offense if your kept pets are still easy to steal.