Jokes aside, here is my review of your current options in the collectible card game category. I'm skipping the very god Slay The Spire because while it's a card game it's a deck building card game, not a collectible one.

Elder Scrolls Legends - The game kind flopped so I don't think it's worth your time. I also think the Elder Scrolls make up for a pretty generic setting.

Hearthstone - Probably the cheapest option as far as card games go, however if you are a new player expect to play cheap agro decks for a long time until you collect enough dust to craft anything more complex. Current expansion and client sucks by the way.

Magic The Gathering Arena - It's Magic, it's online and to my surprise, it works. However, it's expensive and it's still on beta lacking basic features like a friend list to challenge your friends.

Artifact - I haven't played it but from what I heard will be even more expensive than Magic (no freebies at all)  which doesn't sound good to my ears. Still. it's Valve so the production quality may be over the roof.

Gwent - Probably have the best single player content with Thronebreaker. The opinions about the multiplayer aspect are mixed though.

Conclusion: Hearthstone if you are stingy, Gwent if you want single player, Magic overall, Elder Scrolls if you are a fucking hipster and Artifact if you want to believe.