The short version
Progress by measuring what pets earn, keeping enough cash for the risk level you choose, rolling only within that budget, and protecting difficult-to-replace pets before raiding. Reassess the loop after every meaningful gain or loss instead of following a fixed build order that the public data cannot support.
Progression moves through two connected inventories: cash you can spend and pets you can lose. Higher income may justify new rolls, while a rarer or harder-to-replace pet may justify a larger reserve and fewer raids. The best next step changes with what is currently inside your base.