I’m familiar with the absolute basics of networking, but very little surrounding wifi.
I’m current using the modem-router-AP provided by my ISP, along with a couple repeaters. This isn’t working well, and in areas of my house further away from my main AP, packet loss is often around 20% - near unusable. How should I improve this?
I can run some wires (within reason), and have multiple spare routers-APs to work with. I can also buy something new off the shelf if needed, but don’t want to spend more than I have to. What would be the approach I should use? Like, is there a particular type of extender I should be using, or can I use multiple routers as a mesh or something?
Repeaters don’t work, especially on newer Wifi clients. You need a proper Mesh system to cover a larger area. Probably going to run you $300-$500USD for a 3 AP kit.
You’ll need to put that junky AP they sent you from the ISP into Passthrough Mode, hook up the new AP from the Mesh system as your new router, then just place the other new APs in mesh mode as you want them.
If you have multiple other APs and some wires Ethernet ports in the house, you could switch those into AP Mode, plug them into Ethernet, and they’ll act as extensions of your main router as a hacky mesh as well. The problem with this route is that if they are all different WiFi versions and standards, you’ll get a bit of wonky behavior here and there, but it will work.
So there isn’t really a good option, other than buying an off-the-shelf mesh system?
Edited to a bit more. See my other comment.
We can’t see your house, to it’s hard to give you very many options except the simplest.
You will more than likely need more hardware though.