homelab

First time posting here, so please lmk if I should format this question differently or ask for this kind of help somewhere else.

What I'm trying to do: Have two WAPs that each have their own DNS servers. One of the DNS servers is a Pi-hole, and the other one being the regular dns server provided by my ISP.

Why I'm trying to do this: Been messing around with homelab stuff for a while and been having fun with it, and this is my next mini project. I have a crummy roku TV that I want to connect to a Pi-hole, problem is that I cant adjust the DNS settings on the TV, I can only select the network it can connect to. But I don't want to change the primary DNS on my network. I have been messing around with this setup trying to get it to work for a couple days and its been a tough one. I've tried multiple different setups and nothing has really worked. I'll probably type out what I've tried in the comments.

What I have to work with: I have a Netgear Wifi router connected to the internet from my Modem to my WAN port and I have a second Asus Wifi router that I planned on using for the second network which would have its default DNS server be the Pi-hole.

Also please correct me if I'm using terms/concepts wrong because part of the wider goal of my homelab is to have a better conceptual understanding of networking, so I want to make sure what I'm saying is correct.