Looking For Project How do you plan your game ideas?

I’m someone new to game design and I have a million different ideas. Problem is, as someone who’s alone and doesn’t have anyone to help me, I want to know where I should begin! I’ve tried building the frame work and idea for gameplay, but I always make the scope to big and scare myself. Is anyone able to help me figure out the path I should take to figuring out my idea and then sticking with it?