Sunscreen is always a good thing to have with you. The sun in Ghana is mostly high so you need it if you want to avoid getting sunburnt.
2) Sun hat
A good sunhat is also good to have. It also helps you to avoid getting burnt by the beautiful sun.
3) Bug Spray
In ghana there is a ton of bugs flying around everywhere. Therefore its a very good idea to bring bug spray so you dont get stung.
4) Camera!
Its always a good idea to bring a camera when traveling. Also when traveling to Ghana. The country is so beautiful you wanna capture as much as possible.