playing outside of the cage

so I've had my GCC for a few weeks now. He loves to be out on his play gym and is pretty good at keeping himself busy but I'm looking for some ideas of things I can do with him to bond with him and to keep him mentally stimulated. He has on and off days with training, sometimes he wants to and...

My cage sits kind of high (especially for someone as short as I am :laugh:) and I want to build a "cage-top" but not put it on top of the cage? Sort of like a side table play area or a budgie tree? I'd love some ideas from your bird tree, cage-top, or play areas and what your budgies like/didn't...