Follow the listed loop
Begin with training to build Strength and Speed. Then try lifting a rock, collect the egg underneath, and hatch it to obtain a pet.
Keep each action connected
The official description links training, lifting, eggs, hatching, pet income, and upgrades. Move to the next step when the current one is available; the listing does not publish a fixed level or stat requirement.
Use upgrades when progress stalls
The game says upgrades let you lift bigger rocks. If a rock is still beyond your current ability, return to training and use available upgrade options before trying again.
What is not documented
The public listing does not give exact costs, pet multipliers, egg odds, or unlock thresholds. Those details can change in-game and are left unranked here.