If you have limited time in Namibia, it’s best to focus on a single destination, perhaps with a stop or two en route.
Etosha National Park is the obvious place to start and a week is about right to get the most out of the park. It’s roughly five hours’ drive from Windhoek – paved highway all the way – and you can spend a couple of nights in each of the main camps. The waterhole at Okaukuejo Camp is famous, and Namutoni and Halali have great game-viewing waterholes too. Olifantsrus is a new camping-only site in the west of the park, and nearby Dolomite Camp, also new, offers luxury safari tents.
From Windhoek, Sossusvlei can also be visited in a week. Again, it’s about a five-hour drive, initially on tar and then graded gravel. Stay at least two nights in Sesriem and get up before dawn to drive into Sossusvlei for sunrise. If you have time on the way back (and a 4×4), take a short detour to one of the wonderful wild campsites in the northern Namib-Naukluft National Park. Homeb and Blutkuppe are particularly impressive. You’ll need to pay for camping and permits at the Ministry of Environment and Tourism office in Sesriem before you leave.
If you’re arriving from South Africa, then a week-long road trip to the Fish River Canyon is your best bet. Spend a night or two at one of the river-rafting companies along the Orange River and another couple in Ai-Ais Hotsprings Spa. Finish up with a few of nights at Hobas Camp near the edge of the Canyon, and from there it’s only a two-and-a-half-hour drive back to the South African border.