Mali is a hot country; therefore, you should choose light clothing that can be easily washed, preferably made of cotton. Comfortable sandals are the best option in terms of shoes; however, a pair of tennis shoes or comfortable walking shoes will be useful as well, especially for trekking.
For protection against the sun, a head covering and sunglasses are highly recommended.
When visiting Mali during the rainy season a raincoat is a must, particularly if you intend to go trekking in the Dogon country.
For camping nights you will need a light sheet-made sleeping bag. During the cool season a conventional sleeping bag is necessary, particularly for nights on or along the Niger River or in the desert. Some warm clothing should be included during that season.
A backpack is the most practical and comfortable option to tour the country- the lighter the luggage, the better.