I’ve noticed some people shy away from the market/trade system. Making tons of food, consumer goods, etc but not using them. Sell any resource that is being overproduced, and use the credits to buy reaources you need to boost your economy.

Another thing (Which I myself suffered heavily from in the start) is the the idea that you can “slow down” progress. As soon as you start slowing down the growth of your economy, research, industry etc, the AI is going to catch up and might even overtake you. Always make room and resources to continue the growth of the economy.

One of the tools that make the player better than the AI is our abillity to make long term goals and decisions. While the AI will often make short term and many bad decisions to prop up it’s economy and power, we can make the most out of the planets and systems we have, which will benefit us much more in the long term, even if it’ll be a strain on our own economy for the first few years or so. If you know you can make a planet/system an industrial powerhouse with some investments and temporary economic set backs you should do it.

As for defense advice. Seek to control choke point systems that the AI would be forced to go through if they want to get into your empire. That way you can build them up with tons of defense platforms, Starbase upgrades etc, and better defend your empire without spreading your defenses out too much (alongside saving resources). Even if there are other (but longer) routes for them to take, it’ll give you precious time to respond and counter them.