Extender - the easiest and cheapest way to get WiFi elsewhere in your house.

MoCA or Powerline - Roughly the same price. I think MoCA outperforms Powerline, but it changes all the time. MoCA requires there to be a coax jack in both places and works best if you don't have DVRs, etc already using those lines. Powerline has some pitfalls too (at least it used to be that they didn't work as well if the outlets were on different phases, for instance; they can perform poorly when certain types of appliances are running, etc.).

Mesh - Generally the most expensive option (mostly because you are probably going to be buying all new equipment). As easy to install as an extender; a little easier to use since they generally have the same network name etc and your devices (assuming your device is modern and competent) will seamlessly switch nodes. Outperforms an extender. Some will let you run ethernet between the nodes (which is basically just an easy to have multiple access points)

Ethernet - Fastest performance and cheap if you DIY. Need to know a little about what you are doing to do it right (using the right cable type, doing the connections right, installing jacks on the wall if you want it to look nicer, etc.)

You could be like I did for my parents and put one ethernet line in to put your single WiFi router in a more central place. You could be like my buddy who ran two ethernet lines so his mesh system had ethernet backhaul instead of wireless. You could be like me and run ethernet everywhere because you have a giant spool of cable and, at the time, time to do it.