For $50, get Stardew Valley, Steamworld Dig 2, and then another title. If you have a credit card or Paypal on the account and can go over a bit, I suggest Rocket League or Sonic Mania. If you need to stay under $50 with tax, then I'd suggest something like Kamiko or a $10 game, or just hold onto the rest of the money on your account.
Steam: http://steamcommunity.com/id/Bluedestroyer_82/
Online Games: Speedrunners, Payday, Friday the 13th, Dead by Daylight, Rocket League, etc.
Switch: 7518-9635-4492
Online Games: ARMS, Splatoon 2, MK8D, Puyo Puyo Tetris, etc.