Take your time!
This is a complex game, and you need several things done to complete each step before you can go on to the next level of the quest to return home.
AI Cores are rare, to start with. There are also plenty of other things you need to have in place before you are in a position to go into the junkyards.
At the heart of the game is your relationship with your crew. Then it's your reputation/ notoriety. Which means doing missions, helping freighter captains, rescuing slaves, even drug-running! Building up your crew's trust, seducing them and showing them off is also a part of this.
Be patient, enjoy your crew, mine like there's no tomorrow. The rewards will come!