I have a cheap Netgear N300 extender and it works fine. My Google router is in the basement on the far East side of my house due to logistical issues. The only CAT5 I have runs up the middle of the house to the kitchen on the 1st floor and the master bedroom on the 2nd floor. The 2nd floor bedrooms on the West side of the house had spotty signal, and the RV parked out on the West side of the property had nothing. I have the N300 hardwired back down to a GigE switch next to the router. It's plugged in pretty much in the middle of the house on the 2nd floor. The attic would be better, but that would require running more cable. It fills in the gaps nicely - even out to the RV.
Outside I have an Engenius ENS202EXT access point that gets me coverage down to the bottom of my 500-foot long driveway for surveillance cameras. It's PoE and I have about 200 feet of direct-bury CAT6 running to it. It's also plugged into the GigE switch. That AP provides much better coverage to the RV than the extender inside the house, even though it's over 100 feet away. The extender is about 50 feet away, but it's indoors with several walls to get through.
So I guess my advice is if you're looking for coverage outside for the RV, put an access point or extender outside. To fill in the gaps indoors, the cheap extenders work well if they're hardwired rather than set up as wireless repeaters.