Generally, there isn't any "perfect size", since the size varies hugely from project to project.
It depends on the amount of images you use, how well you use them etc.
Some pieces of advice to keep your program's size small:
- Whenever possible, use Tiled Backgrounds instead of big sprites
- Whenever possible, use functions instead of repeating the same code multiple times (no huge impact on file size, but gets more important when your project get bigger)
- Use Tilemaps when possible instead of multiple Sprites
- Try to use many instances of one Sprite instead of using multiple different sprites
- If your game works online, you can load images via AJAX from a server to keep the program size low
There is much, much more to it than just that.
Take a look at this tutorial:
Export time optimization
and at this post.