Option 1 - Routers with Ethernet cable between them
you can get 100ft cat5e cable on amazon for less than $20 and most routers have Ethernet ports on them. If you have an old router already lying around that's all you need. You can extend this beyond 2 routers (I have 4) but you only have 3 non-overlapping channels in the 2.4 Ghz so make sure you don't have 2 routers on the same channel too close to each other. This is a blog post that explains basically what I did.
http://www.hanselman.com/blog/ConfiguringTwoWirelessRoutersWithOneSSIDNetworkNameAtHomeForFreeRoaming.aspx
- First Router
- 192.168.1.1
- DHCP to use the range 192.168.1.3-192.168.1.254
- A wireless channel like 11
- Plug hard-wire into the LAN port
- Second Router
- 192.168.1.2
- DHCP is disabled
- Identical wireless security setup as first router except the wireless Channel. Try channel 1 or 6 if the first is 11.
- Plug hard-wire into the LAN port (not the WAN port)
If you are lucky enough to have a router that supports dd-wrt you can follow the guide here https://support.flashrouters.com/setup-guides/advanced-wireless-setup/wireless-access-point/
If your house is not already wired and you don't want to climb in the attic, there are powerline adapters that let you use the power lines in your house as network cables. These cost a little more than wireless repeaters but if you already have a 2nd wireless router you can get better throughput and lower latency.
https://www.amazon.com/gp/bestsellers/electronics/1194444/ref=zg_b_bs_1194444_1
Option 3 - Use an range extender
range extenders are easy from a wiring prospective but you don't get the seamless roaming and when your using the repeater you have to make two wireless hops (1 to the repeater and one from the repeater to the router). If your router does not support open source Firmware like the Neatgear WNR3500L you can buy a dedicated wireless repeater for $20 on amazon.
see How to Extend Your Wi-Fi Network With an Old Router
