April, where are you based, US?
If it's in the US then B&H for photo kit, Cabelas or any US outdoors will do, but avoid the 'safari' look. Also what time of year are you going, as that will dictate what to pack clothes wise too. Also check if you need any 'jabs' & Malaria tablets, Malarone is good, but double check with you Doc or Pharmacy.
There will be plenty of Tour operators offering 'escorted' trips i.e. A&K, Expert Africa etc, plus there are also other more tailor Photo operators too based in SA, i.e. two ex Members of BPN (Wildlife) that come straight to mind or a continued BBC Wildlife of the Year winner too, who runs operations out of SA. If you want Botswana there is also two more ex BPN's, great guys who know their stuff and you would have a ball. The hardest part is to choose the destination, then start to 'drill' down so to speak, as planning is key.
If you want more info or help then shout, happy to forward their details on too.