[Thomvis]

In my own experience, it is not only about starting simple, but also finishing it simple. I know you're not saying it isn't, but what I want to emphasize is that it is too easy to say that you're done with something simple and then move on to the next/bigger thing. For example, what eru suggested, if you build a Tetris-like game. You probably can have the gameplay finished in a few hours. And then, move on? Or spend another week on polishing, menu's, sound, graphics, copy, etc. I think the most valuable part of the lesson of starting simple is in finishing it. (And they don't tell you that.)

[brador]

This is probably the best hidden advice on this page. Build complete projects. Make it a habit. If you just make gameplay prototypes, that will become your habit and you'll struggle to ship your big idea when the time comes. You'll be missing the final 90%. You won't know how to prep game art for example.

This applies to all creative "package" projects. Learn to ship.