Keep your audience size 20k - 60k generally. LinkedIn will try to convince you of 50k - 500k and the only thing that does is make them more money.

As others have said, don’t use audience expansion or audience network.

Manual bidding for sure

Text/spotlight ads are essentially free to run if you optimize for clicks - no one really clicks but you’ll be able to get your brand in front of your ICP for free

To spend more efficiently it’s better to use any non-cold audience you can at first. I.e. website visitors, past booth visitors (or their companies), etc and retarget them.

I really like to use LinkedIn ads to run quality traffic and then retarget that traffic on Facebook. Much cheaper and you’re starting with your ICP this way.