You will want to build two enclosures, one a raise-up cage that will house the animal for its juvenile time period, and one to house the animal as an adult.
The rule of thumb for a minimum enclosure size is twice the length of the animal wide, once the length of the reptile deep, and enough height to provide at least a foot to two feet of soil substrate on the bottom end and climbing room on the top end. Of course, this is the minimum and as a responsible owner you will want to provide more than the minimum.
You will want to plan the raise up cage to provide several exponents of growth and not be limited to one small size.
Since the panoptes/gouldii/flavirufus breeding is so muddled, it's hard to know what you're getting beforehand, and you will still be looking at 3-4.5 feet TL for sexually mature animals depending on sex and genetics.