I'm not nearly as into world music as I used to be. It's been a long time since I've listened to any of the music from Africa that I own and I never went too deep into Highlife. I bought a comp on the genre I think from Rough Trade that was pretty decent, Eric Agyeman "Highlife Safari" and a couple of albums by Joe Mensah. If you're looking to buy something, a comp is probably the easiest way to go initially. E.T. Mensah (unrelated to Joe Mensah) is probably the biggest name in Highlife. You can find some of his stuff on Spotify if you want to sample. That Eric Agyemen album is on spotify too. If you've never heard Highlife, the best comparison I can make is to old school jamaican ska but a little more jammy and a little more guitar centric. You'd probably like it.
There was some Afrobeat in Ghana too. African Brothers and Ebo Taylor are two of the biggest Afrobeat artists there.
These are two good comps:


both are on spotify.