I'm not sure if I understand your 1st question well or not. So feel free to let me know if this response still doesn't answer them!
(1.) Getting a minipet for your pet: I'm guessing you're saying you went to the minipets shop here: https://www.marapets.com/shop.php?id=22
you can buy minipets there. but some come from other places (like account upgrades, events, etc.). If you ever want to check where a minipet/item is from, you can click the "check price" when looking at it from your inventory and it will say underneath where it comes from.
to add it to your pet, click on the minipet in your inventory. Then click "use item".
(2.) Creating a club: You should see an area to "Buy a club" for 15k mp on the clubs page here:
https://www.marapets.com/clubs.php
Otherwise, you can check out the notice board to see which clubs are looking for members here, if you think you'd like to join any existing ones:
https://www.marapets.com/forum.php?id=6