here are some tips im on world 4 btw sunny get the double hand strenght and double knuckles and bicep get the the pack from the shop it doubles the amount of strenght u get and u can get 32 pets equiped so get the halo egg the heaven one the best pet there 0.5 is 1500 boost
I at 6 world I have tips for u, best way to grind strength are the grip and bicep if u have so much bicep strength u can equip the best dumbell and at 5 world just do bicep training