If you want something in this National Park there are 2 rules:
1) You have to bring it with you
2) You have to take it back out
There are absolutely no facilities in the Park for humans in the Park except for one squat toilet at the entrance. Between the heat and humidity you will need at least 2 litres of water per person. Also food. I took some bread in with me and the 2 amused rangers opened up fancy energy bars. Mine costs less, but you will need food. Tracking the Gorillas can take 2-5 hours just to find them. Then you get 1 hour with them and its 2 hours back. The amount of calories you will consume will be very high. This is due to the altitude, incline, rugged terrain and distance. You may want to purchase some fancy energy bars to take with you or just take bread from your hotel at breakfast. Loads of butter and honey on it for the energy. Either way you need food and water.
Make sure you don't be completly stoopid like me and forget your waterproof jacket!! On our way back from the gorillas it started bucketing down and yes, I was extremely wet and cold.
Long trousers and 3/4 - long sleeve shirts advisable, because of the sun and plants flinging on you and scratching. Good hiking boots are essential also.
I had heard about taking gardening gloves (but didn't) and found that this was an item that you didn't need. You just need to watch where you put your hands.
Photo Equipment: I had my digital camera and took so many pictures while we were with the gorillas. I did keep in mind to make sure I didn't only see them thru the view finder. It's hard cause you want to get the perfect pic, but you need to experience the gorillas while you are there also.
Miscellaneous: Don't forget to take enough water with you for trekking. You never know you may have to trek up to 7 hours like we did and it got bloody hot!