Budgies are birds. With wings.
Birds fly high and wide, looking for food, shelter, mates. They must surely adore the effort you put into choosing the right plastic mirror for their wire shoebox jail. As said earlier, just setting the poor thing free does not absolve you of responsibility for the life you have bought and now claim mastership of. If you do not have the time to spend with an animal so it learns to share your space freely, why did you buy it? To prove you can afford it? Because it was sooo pretty? Well, congratulations, you afforded acquiring that beautiful, innocent life, now care for it. If you cannot share your habitat with it, either

build it a habitat, or get rid of the animal in a responsible way. And note we insist on a habitat, not an enclosure, camp or cage. Of course, the only difference between a camp large enough and an actual habitat, is the thought you put into it.
Budgies love to browse greens, so grow some greens. That very same expensive seeds you bought, can be sprouted in a dish, and left on the floor for the budgies to chomp down. Once a week and you will already see happier birds than anyone in your neighbourhood. It takes very little effort to put seed and water into a shallow dish filled with sawdust, waiting a few days, and carrying the dish to your birds, come on, show some budgie love there.
Of course, by judiciously choosing which plants you destroy in your garden, you can grow fresh food whole year round. Just because a grass does not look like lawn, does not mean it is your enemy. Eat the weeds, brothers and sisters, eat the weeds, and the animals around you will clean up your leftovers. I shall post some pictures of grasses our budgers really appreciate. Besides, how can you live without chickweed, one of the most nutritious salad greens out, and your birds will fight you to get there first. Of course, there is always dandelion. If you really have no plan for that most marvelous of medicines, feed it to your birds, they eat every last scrap, EXCEPT THE ROOTS. NEVER ANY ROOTS, REMEMBER?
So, the place must be big enough to allow the budgies freedom and excersize. You planted some potted greens that can be taken out to recover while a new pot supplies greens for a few days. Now you need nesting spaces.
Budgies are forever nibbling, and many breeders have success drilling holes into sisal stumps. The bird will then enlarge the inside, hollowing out a nesting space. On sale you will find a multitude of square wooden boxes, usually made from scrap chipboard. They work perfectly well provided they don't get wet, and they are only good for one season or so, before they nibble a hole right through the soft wood, dropping eggs and babies on the floor, or just simply dying off due to the cold draft. We once temporarily secured a breeding mama without disturbing her, by wrapping the outside of the box with thin metal sheeting so the babies stop falling through the hole in the floor. Our breeding boxes mount outside the cage, and we lost a few birds before we realised where they are escaping. It is a cage we got for free together with the budgies, they were urbanisation refugees, their owners had to move into a more expensive abode, all modern and not enough space to swing a cat. We mounted the boxes outside so as not to waste the limited space inside. That's how Greenpets roll. Also, we can peek in on the hatchlings without disturbing anyone in the cage itself.