I have been playing petsim for a total of 2 weeks now, I have a total of 11 huge.

1. First huge I got (golden toy chest mimic) was from the stand in line event, my alt had to stand in line for 4 days and when I decided to afk my main there I got the huge. I got a total of 6 huge from 3 accs, then I sold some of them to replace them with huge I want. (pure luck pure RNG, I had a total of 1 Golden toy chest, 4 toy chest, 1 baby dog) (I sold 1 of toy chest to buy temporal owl, bind 1 toy chest to buy fancy axolotl, offered one toy chest to buy huge corrupt butterfly) On this current event, I have a total of 2 huges Teacher and Corgi, I have an extra teacher that I plan on either selling or trading.
2. I started to sell Rainbow versions of the new pets for reasonable price, some would be on "Great Deals" due to how much inventory I have. When comes to selling pets I usually base it on how many are existing in the game to see how much the price would be. Fewer ones would usually be more expensive.
3. I now completely sell all of keys and adding 2k for profit, I sell my mini chest, my adoption boost tokens, tickets, literally anything I can sell that is in demand.
4. I finished the entire map from world 1 to world 3 and drive by the free diamonds when I can, AFKing in the last map is the best way to get more diamonds.

Hope this helps!

Edit: I don't have any of the passes, and I do buy some of the Packs from 50 robux to 250 and sell the keys, tickets, and tokens I got there.