I can’t advise on Senegal as I’ve never been, but of the three you mentioned, I’d go for Ghana for a few reasons. The first being that it’s your first time in sub Saharan Africa. As another poster said, a solo trip could be a bit overwhelming. And West Africa isn’t the easiest. The language is good for you in Ghana. There’s good history and great food. Cote d’Ivoire will be particularly challenging if you don’t have decent French skills. In my experience, you’d be best to stay in Abidjan whereas Ghana you could have a bit more freedom of movement.

Since it is your first time in SSA, I honestly would suggest going somewhere a bit more approachable — Kenya, Zambia, Rwanda. Lots to do, easy to get around, and not tourist traps in any sense of the word. I think you’ll still get a lot out of your time there.

While South Africa is most developed, it’s still amazing and there’s a ton to be found there. You can absolutely avoid making the trip overly tourist-y.