Shadowverse

I still don't have any scenarios. But they are cool. At the very least, the Skellige and Nilfgaardian ones are now essential maps if you want to play with those classes – they are powerful. The Elven and Monster ones are good maps, but not essential; you can play without them. The Northern one is only useful for fun decks based on machines. I haven't seen the Syndicate one in the game at all, but the Syndicate isn't very good overall right now.

As for strategies, the Nilfgaardian class strategy (collar) is very strong. The Elven one is very useful, but I'm doing fine playing Harmony without it. The magic lamp works well in many decks, but I don't think it's essential. I wouldn't craft the others specifically, at least not yet.

Added 6 minutes later
The expansion was really unexpected, and I didn't save up for it at all. But I'm glad that decks with the Lavka are playing well: I crafted Radye, Matta, and now I'm enjoying the game with almost any class.