I would suggest investing in a nice sleeping bag with a temperature rating of minus 20 degrees Celsius. You’ll also need a decent mattress of some sort – if you’re bringing your own gear (it’ll be carried by porters), a Thermarest will suffice (self-inflating mattress). The tent, mattress, and other essential equipment are frequently provided by the business through whom you make your reservation. Before you travel to Africa, you must determine what they will supply.
Above 3,000 meters, it will be chilly, and it will be quite cold in the final camp and on the final ascent. For the last ascent, I had top-of-the-line thermals, a down jacket and overpants, excellent quality gloves, and double caps. It was windy and chilly.