Must do’s when setting up a network

Apologies if some of these questions are silly, I’m setting up a new network with a gl iinet router flint 1800 I think.

My last network was pounded with dns queries and I ended up messing around with the settings that much that there was a privacy warning and the network was blocking dns from being encrypted.

Also with it sure how to isolate devices like cameras etc the admin page is pretty messy to navigate but really have no idea what I’m doing. Is there any advice to build a solid home network? Security is a priority. If any recommendations on how to monitor the network such as softwares or apps. I would like to have a strong firewall also. Thanks for any help