Marché du Niger, in the heart of old Conakry near Avenue de la République, is the city's central market and the easier counterpart to the vast and overwhelming Madina market further north. It sprawls across several blocks of stalls and shops, selling fabric, food, household goods, traditional medicine, and a steady current of mobile phone accessories.
For a first market visit, this is the right one — less intense than Madina, walkable, surrounded by other things you might want to see. The fabric stalls in the eastern section are particularly good; Conakry's tailors are skilled and quick, and a couple of metres of wax-print from here can be made up into a shirt within twenty-four hours. Watch your pockets, particularly in the crowded inner aisles.