Steps for cheap gaming:

1. Add Humble Bundle and Fanatical to your browser’s bookmarks. Check them every week for new bundles.
2. Register at Epic games. No matter how much people hate’em, you’ll be getting one to two free games per week. Some of them AAA titles, or even better. Yeah, no kidding: the whole Batman Arkham trilogy, the whole Bioshock collection, etc.
3. Since Epic-isn’t-Steam, those games won’t be “launchable” through Steam’s UI on your Deck by default. Switch to Desktop Mode, install Heroic Games Launcher or Lutris from the available software, and follow the instructions to add Epic games to your Deck.
4. Whenever you see a game you like ANYWHERE, make sure to add it to your Steam Wishlist. THEN…
5. …pay a visit to IsThereAnyDeal and login with your Steam account. You’ll also have to set your Steam profile to “public”, IIRC, for IsThereAnyDeal to access it. Then, go to your IsThereAnyDeal account’s settings (which will have been created when you log-in with your Steam one), add your mail, and enable email notifications.

Result: Free games each week and daily updates in your Inbox for whenever games you want have dropped in price.

Enjoy!