Having many different sized and shaped perches in your budgie cage or aviary is very important to stop issues like arthritis and bumblefoot. You can use round and square dowel, rope perches, natural branches from safe trees. Check out these links Discussion on Safe Wood and Safe Wood There are also calcium perches and many more that are available from pet stores.
Do NOT use sandpaper on any type of perch as this is very bad for their feet.Adding perches at the sides leaves the middle section of your cage free for flying. This exercise is important for the health of the budgergar, so try not to overcrowd your cage/aviary.
Do not position them over water or food containers as it can be contaminated by their droppings. Placing your food containers in a low position, with the perches at different heights, will encourage your birds to use all the space in their cage, giving them added exercise.