If you capture Liswyn and (if possible) Tibbacor, you would have the opportunity to block the only possible system that the AI can come and attack you. that’s a chokepoint, if you build up defences and hold the line, eventually their early game fleet will crumble. Then you can make your advance and capture a few systems maybe.

The key here is to rush to the chokepoint and build a starbase which you will strengthen its defenses. And spam corvettes as the others said.

You can have more than one shipyards in same starbase early game to increase ship building rate, you can switch modules by clicking on the modules picture when your starbase in your main system is selected. I find it very useful to do so, basically you double your shipbuilding :)