Visa is given on arrival at Zanzibar International Airport to Nigerian citizens and costs $50. You can also obtain your visa before traveling at the Tanzanian embassy in Abuja. You would typically want to get it before hand to skip the immigration queue but if you aren’t able to do so, you can just show up at the airport.
An economy class ticket to Zanzibar would cost you anything from N100,000 – N150,000, depending on when you book or your travel time.
Edit: a recent check put flight costs within the N220,000 – N250,000 range.
Taxis from the airport can be arranged by the hotel you choose to stay at. Budget $35 for a trip to Stone Town, $55-75 for a trip to Kiwengwa, Paje and Jambiani and $65-85 for a trip to Nungwi.
Food & Drinks
We spent about $120 on feeding for the entire 6 days. Breakfast came with the room while our lunch and dinner were quite basic and cheap. (Except for the last day when we had a fancy 4-course meal)
We took a day trip to Stone Town and Prison Island with a Spice Tour en route. This was organized by the hotel and it cost us $50 each. This was basically the only thing we did in Zanzibar. A snorkeling experience was underway but we wound up cancelling. The price for that was about $60.