Setting up a sub LAN

Hello again guys. I'm no noob but no expert. This is what I want to do and you tell me if it's possible or not.

I want to use a dedicated IP to run another network via my main LAN. I basically want to use a local IP as a WAN port with another router attached to that. I have so many IPs floating around on my network, I would like to clean it up a bit.

This is just extra info on my setup, so read no more unless interested.

I have a wireless router set up as a bridge to my network and...

Setting up a sub LAN