We have an incredibly active and helpful community, so be sure to join the DragonRuby Discord Server.
Here's a walkthrough of the Low Res Project Template that is available as a sample app. It'll definitely give you a solid starting point if you plan on entering Nokia Jam.
DragonRuby is a commercial game engine for building 2D games (it can do more than low res games). Here's a tech demo and tutorial to show off what DragonRuby Game Toolkit can do. It's a solid option if you plan on entering Global Game Jam 2022.