It really depends on accessibility to running cables. Don’t cheap out, run CAT6 at the minimum. If you think you might need an extra run to your media center, RUN IT. I prefer my AP’s ceiling mounted and even if you don’t have the money for the AP’s themselves, run the wire now. Think you only need a 8 port switch, get the 16. Make sure you have plenty of receptacles for all of your devices and plan to have a UPS powering those critical devices. Networking devices create heat, make sure they can breath. POE is your friend, have a switch that is POE. Learn about VLANs and make sure your router supports them in order to separate your secure networking devices from your IOT and guest wireless network.

If there's a space behind a wall in the attic that you slithered into 10 years ago to run power for a ceiling fan, don't assume you can still slither into (and out of) that space as easily now to run Ethernet cable.

There's a chance that you will find yourself faced with a choice of calling the fire department or killing yourself trying to climb back out backwards.

I managed to get out without assistance.