/u/Mifuyne said it better than I can. "Big Ideas" almost never work for a first-time game. It's usually safe to assume, most big published games have taken teams of people multiple years to build. I have some experience, but big ideas are still always my downfall.
Your first game should be a learning experience, and you should aim to finish as fast as possible, while still doing good work. If you are set on a platformer, try an auto-runner like the other comment suggests, or look at arcade games. One level from Donkey Kong or Mario Bros (not Super Mario Bros) is about the limit of complexity I'd suggest for a new dev. Even NES games like Super Mario Bros are pretty complicated, and would take a new developer many months. And there's no shame in copying a classic game's mechanics for your first game.
Overwhelmed in what way? Too much to learn, not enough coding knowledge, or something else?
And what types of games are you trying to make? Certain genres are harder or easier for beginners.