You earn Shop Tickets by completing achievements, ticking off missions, participating in events, and as thank-you gifts from other players you've played against in Versus mode
The Haki apps scanner and the card detail pages both show the variant code (the -v2 , -v3 suffix)
Other editions can be valuable as well
Cards like Piru, the Volatile just tickle the Timmy in me
If the sacrificed artifact was legendary, draw a card
To actively mill your opponent, youll need to catch them with Didnt Say Please, stick an early Eye Collector (probably the most important enabler), or suffer playing Merfolk Secretkeeper (a combination of very two underwhelming cards, Tome Scour and Kraken Hatchling)