As for the season... difficult to advise really. Everyone's got his own preference... In winter you can have great sightings throughout the day.
It's cold and the critters are on the move. But that also means you are even more reliant on "the right time, right place" thing, because the
animals often don't hang out. They do their thing in the riverbed and vanish into the dunes again to get cozy and warmer
Summer can be extremely hot with temperatures reaching almost 50°C. Even worse on a rainy day when humidity makes the heat almost
unbearable. You have to be early to catch the animals and stay out as long as possible to have them moving again for the the night.
(Mind you, gate opening in December is from 5.30 to 19.30 - makes for looong days and short nights,)
January can still be hot and is the least popular when the availability of the sought after camps is anything to go by.
March and April are quite good, in my opinion. May probably too, but it can get nippy already. September is popular but can also be coolish.
October and the first half of November are pretty good too, with temperature usually not being as bad as after mid-November onwards.
As for the camps: If you want to afford the stiff rates (ZAR 1745.00 for a cabin in a wilderness camp at the moment), my perfect 10 day itinery
as a newbie would be: 3 nights Kieliekrankie, 3 nights Nossob, 4 nights Urikaruus.
I'd definitely avoid Twee (entrance camp, very busy and too loud for my taste) and Mata (there is the Kalarahi Tented Camp close by instead which only has 14 tents).
, even if I far prefer the Aoub River Valley and if you need to charge something and do some shopping. (I am sure though, that you have a charger 
