Start off with a goal of getting to your 2nd dome. Until then, import machine parts and electronics, and only as many polymer as you need to get each new dome built. Get extra parts and electronics, but never build anything that needs polymers.
Your first factory should be Machine Parts. It should go into your 2nd dome. From this moment forward, you should never have to import machine parts.
Your third dome does polymers. From this moment forward, you should never have to import polymers. Keep making sure you have a stock of 20-25 electronics when you unload a rocket, and ask for another 10-20 each time you drop down to 10.
As of your 4th dome, you should be able to finally build your Electronics Factory. Make it the #1 priority for that dome, keeping that factory fully staffed (yes, all 3 shifts).
Basically, you just have to move a little slowly and don't take your imports for granted. Prioritize Machine Parts and Electronics because of just how crucial they are to your extractors and drones.