Firstly you want at least every pet on tier 1 for their bonuses.

Also the only stages you need to 3 star on are the pet reward ones.

Stage 1-5 = T3 SW, two units of your choice.

Stage 1-10 = T3 SW. six units of your choice.

Stage 1-14 = Two Senior Infantry.

Stage 1-20 = T1 Wolf Warrior, T1 Ninja (senior of each would probably do)

For the other stages just use what makes sense and spam all the strongest units you have.

The stages you'll be using your tickets on are the pet reward stages so they're all that really matters.

I also suggest spending guild coins and honor coins in the pet shop if you have an abundance like myself.

Lastly, do a quick revive past stage 250 and you'll receive the "Mambo" Pet for free. He'll apply a quest gold buff of 300% at tier 1. I believe setting him as your main pet will double that to 600%.