What I am doing at the moment, is sharing the internet through my wifi to the ethernet cable. Windows gives an IP of 192.168.xxx.xxx (xxx are for security reasons) for the ethernet, so is that IP the gateway for other devices, because they don't have wifi to connect to the router, at the moment, I don't have access to the router
192.168 ip addresses are private IP and everyone uses them they mean nothing really.
Sounds like you are using ICS. When you do that the PC is acting as a router. It will create a new network and give out IP addresses to the device you are sharing the connection to. It is pretty simplistic compared to a actual router but it will in your case share the IP you get via wifi from the main router with the device you have attached via ethernet. To the attached devices your PC is your router and the gateway.
ICS is not really something you want to do unless you have no other option. You have made a expensive pc into a very cheap router. You have to be very careful what you run on the PC when you have the sharing active to not cause data spikes on the connected devices