If the bird will be spending several hours a day out of the cage, you don't need the largest cage made. If the bird will almost never be out, buy a cage it could fly in. In any case, the cage should be large enough that the bird can spread its wings without touching any wall or the roof. Be sure the cage you choose has no sharp edges that could cut you or the bird. Try not to buy a round cage, because the perch arrangement causes the bird's tail to rub on the bars and get worn and ugly.
Most round cages are also awkward to fit paper into, and difficult to clean.
Whatever cage you buy should be both convenient for you to care for, and healthy for the bird. Perches Perches should be of different shapes and thicknesses. Birds stand on perches all day, and if they always stand on the same size perch, their foot muscles will stiffen from lack of stretching. Some birds also will get sores on the soles of their feet from always standing on the same points. Cut the branches, wash and scrub them thoroughly with clear water and Oxyfresh Cleansing Gele or Oxyfresh Dentagene , and bake them for 30 minutes at 350 degrees to kill any insect larva or eggs.