If you’re trying to save money between Cape Town and Joburg (including virtually everywhere along the coast), you need to consider taking the Baz Bus.
The Baz Bus is a “hop-on hop-off” service between backpacking hostels (which will also save you money) around South Africa.
The service stretches across the southern coast of South Africa and makes stops at over 180 hostels in more than 40 cities, towns, and villages.
For more out of the way places, the Baz Bus also connects to several private shuttles along the way.
You can buy the “hop-on hop-off” ticket to your final destination, get 7, 14, or 21 day passes, or book special tours and wildlife packages.
South Africa also has a well-developed backpacker scene, so you’ll be riding with people who are also travel enthusiasts on your journey.
Here is a video that shows you a bit of what to expect.