You mention wireless and extenders. A powerline adapter is not a wireless extender. It works in such a way that it will either work great for you or not at all. They're all pretty much the same. You probably won't see anywhere near the advertised bandwidth, but as long as you get a signal at all, it'll be more stable than wireless.

If you don't get a signal at all, try moving the devices to different outlets until you find a signal. It is heavily dependent upon how your home's electrical wiring has been run.

I used the NetGear powerline adapters at my first apartment. As smaka said they won't get the advertised bandwidth by any means, but in all honesty it worked great for gaming. It was way more reliable than wireless and ping was solid...the few times i plugged directly into the modem the ping difference was only 2-3ms. I used mine for almost 4 years without any issue.

I bought the Netgear XE102 model...which was the first one available at the time, so i'm sure there are better ones out there now. You can get a used pair of those on ebay however for like $20.

Powerline networking is extremely dependent on the condition of the wiring in your house. If you have a super old house and every outlet is just replaced with GFCI instead of a rewire it's probably going to be garbage, otherwise it's worth a shot and is usually better than playing on wireless.

It's a lot cheaper to just buy a really really long ethernet cable if that's still an option. KBlair is right about powerline and wire condition, so watch out for that.

Wireless became too unstable for me so I went the route of a long-ass ethernet cable (I'm talking 100 feet) and ran it through the house from the top floor where we have the internet set up to the basement where my pc is. It was about 60 bucks for the cable though, so that's a bummer. Also it's visible on the stairs and stuff and could be a tripping hazard. Got a bunch of u-bolt fasteners from an old hardware project and put the cable off the ground so no one would trip, worked out ok but ugly as heck.

I use a powerline adapter to play tf2 when I'm home. The house is about 20 years old so the wiring is all good. My computer is at the opposite end of the house so if I was on wiki I would drop from a game very often. With the powerline though I don't think I have d/c'd once. Thoroughly recommend.

based on these responses I'd try getting adapters from a vendor with a good return policy. likely better than WiFi extenders

I'm using one right now because I can't run a long Ethernet cable to my PC. Seems fine so far. Ping's stable and I'm getting decent speeds.

adds 5-10ms ping for me, occasionally disconnects (not often) for like 10 seconds (my house is huge btw, like out of range of wireless N signal)
anyway the powerband is better than wireless, worse than a long ethernet cable.
imo its playable (wireless isn't)

I have used powerline adapters in the ass end of nowhere to get internet in a different building (only a few yards apart, but still) on a setup probably over 50 and still it worked like a charm. 10/10 would recommend. In my experience the one thing they really do hate is sharing a plug with a bunch of different appliances.

Me and my brother used to use them, we had a 60+Mbps download package, but with the powerline adapters we only got 30Mbps.