If you want to go Unifi, you can start in the $120 to $250 range and step it up as needed, you can buy
1 lite disk (access point) for $99 or 1 long range disk (access point) for $179, and place it at the opposite side of the house from the router. See if that gets enough coverage. The more walls there are, the less distance the signal will travel, so the best places to install them are on the ceilings in hallways, or in big open rooms (that don't often have shut doors). If you use the POE feature (highly recommended), you will also need to buy a powered switch or injector (described in brief, below).
EDIT2: For a full Unifi setup, you need a bunch of stuff, like a controller to house the software, called
a cloud key, a replacement router, a switch, etc., but (according to the internet) you can just add an
access point for $100 and a PoE injector for ~$10 to get started. Once the access point is on your network, you can use the Unifi app to set it up.
How that set up would work look: Outside Internet connection -> (Cat6 (or Coax, depending on service)) into router -> (Cat6) into powered switch -> (Cat6: long run) into access point (Unifi disk) -> (wireless) into to TV
My unqualified and amateur opinion: Two of the $99 lite disks in halls close to the opposite corners of your house (from your router) should cover everything, but 1 might do it. If you buy just one first, you can kind of test it out, by running a long Cat 6 on the floor, to wherever you think it may work, and hang the disk with a small nail (or on one of those double sided tape hangers) on the wall closest to the celling mount (if you are putting it on the celling). Then walk around with a laptop/tablet/phone and measure strength. TVs usually have cheaper receivers than phones/tablets, so defiantly check them too.
There are some tools out there, that if you upload your floor plan, they will inaccurately estimate coverage, but I have never used one, so don't know much about it.
Reference:
POE is power over ethernet: It allows you to use a
powered switch to send the power as well as the internet connection through the Cat6 line and not needs a separate wire and outlet to power the device. EDIT: You can inject power into the Cat6 run using a
PoE Injector for $6 to $20.
PiHole is an add blocker for your whole network, but it is easy to look up, so I assume you already googled it.
