For $50 I’d get (afaict current prices):

• Hades ($7.49)
• Pathfinder: Kingmaker ($2.99) (make sure to force-enable the Windows build on the Steam Deck, the Linux build has issues with gamepad input on the kingdom management screen)
• One Deck Dungeon ($1.99)
• Slay the Spire ($2.49)
• Wildermyth ($16.24)
• Against the Storm ($8.99)
• Terraformers ($7.99)

This totals now $48.18. If you have an additional dollar to spare, I’d also recommend to get something to scratch that retro-gaming itch:

• The Settlers 2 ($2.73 on GoG - needs DOSBox, for which I’ve written an install guide)

That’s now $50.91 in total.