More details would help. Do you currently have a system installed? If so, what controller(s) do you have? If not, you would need a controller, a receiver, and possibly a transceiver (depending on what type of controller you want). The easiest option would likely be a relay controlled in-wall module such as a XPFM
https://www.x10.com/products/xpfm, a transceiver module such as TM751
https://www.x10.com/collections/x10-wireless-transceivers/products/tm751, and a transmitter such as KR19A
https://www.x10.com/collections/wireless/products/kr19a.
There are lots of options if you choose X10, this is just one possible configuration that would be a lower cost option. If you are not invested in the X10 ecosystem, I think I'd recommend a different option personally. I think an ESP based option would be the cheapest and easiest and works with your existing WiFi and phone. I have tinkered with Sonoff and they seem pretty popular. Those modules start at around $5 shipped from China and you are likely looking at $50-100 for X10 depending on options.