what router are you currently using? depending on how old it is you might get better speed with buying a better router.

Im not 100% sure if you can connect two routers to a modem. Even if you can connect two all the same traffic will be going though the modem after.

Its a netgear r6200v2, its a dual band but theres also about 25-35 devices connected at one time, which is ridiculous. Ive thought about purchasing a tri band router but im sure if that will fix the problem. I also live in the basement and the router/modem are both located above me so thats not great either.

You must have a big family to have 30 devices connected simultaneously. Even if you do have that many then theres not much of a reason to have your own private network unless you plan to stream porn across it and are scared your parents will see.

Whoa man I watch porn righteously alright and i do have a ridiculously big family who all each have an Xbox one, iPhone 6, tablet and or PC so yes i definitely need my own private network.

I still fail to see why you'd need your own network unless you're completely certain your current router is saturated. If you think it is then you could get a switch for your room then wire that directly to a Gigabit port on the router and forgo using WiFi. If you feel mean you could even split the 2.4Ghz and 5Ghz frequencies and use one of them exclusively for your wireless devices. That would show up as a unique SSID but would operate through the same router.

If you wanted router level you can configure an additional subnet, but you wouldn't be able to see any other devices on the network. Adding another router to the modem would be a pretty clunky way of doing things and you'd likely increase interference by a small amount too.

I would: Push family members to 2.4Ghz spectrum if they aren't too worried about speed and use the 5Ghz band for your devices and use a cheap GigE switch for wired. Aslong as your computer is password protected they wouldn't be able to access any drives or printers anyway so don't worry about the porn unless they are committed to packet sniffing.