Just be aware that each time you move will add to the costs and takes time. Regional flights and transfers to a lodge/reserve can cost 50-100% of your nightly budget (e.g. if you take bush flights).

A typical itinerary for Southern Africa is often to fly in to Vic Falls. Spend 3 nights, 2 in Kasane / Chobe doing river cruise and day safaris and 1 day to see the falls. Then fly direct to Cape Town for 3-4 nights to see a few highlights and penguins, then fly direct to Hoedspruit or Nelspruit and transfer to 3-4 nights in a private reserve in the greater Kruger area, then fly back via an evening flight from JNB. It is whistlestop but you see three different areas.

From what I know around the Kruger NP area, the top end lodges that have luxury lodgings but also well-habituated wildlife and usually limit to 6 people per vehicle are probably outside of your budget. But there are lots of very good lodges with great wildlife viewing. Look at Manyaleti, Timbavati and Klaserie reserves, lodges like Bateleur, Simbavati River or Trails, Xanatseni, Motswari Private Reserve, Elephant Plains or Nkorho. That should give you an idea of the facilities and how the drives are done. Or if in winter (May-Aug-ish when you shouldn't need air-con) the Honeyguide tented camps or nThambo tree camp. If you don't want to think about anything, you can arrange transfers to these places. But you will save money if you hire a SUV type car from the local airport and drive yourself in.

A very affordable, community focused effort is Tembe Elephant Park, in KZN, who can arrange a light aircraft transfer. And if you are willing to drive, it can be combined with a few days on the beach.