See if you can get a second-hand copy of 1-2-Switch cheap. It’s actually quite good and a lot of fun as a party game, but definitely something that should have been bundled in with every Switch, rather than something you have to pay full game price for.
I’ve heard good things about Death Squared as a party puzzle game, and for currently 90% off in most regions’ eShops, you can probably pick it up using just the Gold Points rewarded from buying other games.
Both Crypt of the NecroDancer and the Switch exclusive Cadence of Hyrule crossover have 2-player local coop. Crypt of the NecroDancer gets huge discounts (80% off) pretty frequently, Cadence of Hyrule not so much.
Also, I’d recommend checking out and bookmarking Deku Deals. It’s a great way to find games that are on discount as well as price history.