Happy and joyous new years Jessy!
Africa is really much more expensive than most would expect. So here's a quick breakdown of things:
$10 - $15 for dorm in beautiful backpackers (They're mostly in really stunning places)
$10 - $40 for twin rooms/ private rooms in local guesthouses. Sometimes nice, sometimes... well...
You can always get a prepaid sim for $1 and buy internet bundles. I would estimate about $5 per GB on average. Some countries are cheaper, and some more expensive.
If you buy huge bundles, it'll be way cheaper of course.
That really really depends where you go. If you travel across local villages, towns, cities... well, there's mostly meat and heavy meals for $0.50 - $2.
If you look for healthy food, your best bet is South Africa and the capitol cities of most countries. Where ever there are lots of expats or tourists, there will be a nice (and western priced) place to eat
There's so many factors but and depending on your standard you can live on a shoestring or really expensive. Also depends how good and smart you are in making decisions. And how tough you are when it comes to transport, accommodation and food.
Any budget will do it. But if you want to see national parks, you better come with a good amount of savings. Many entrance fees start at $30 - $60 a day.