Patience :) Awesome set up.
Is the frag tank connected to a display? If it is you can move pretty fast. If not, I would add a few beneficial fish (algae eater, wrasse...) to help with bioload. Then I would wait a bit to see some coralline algae starting. Then I would add some easy stuff - zoas, LPS. Then a few easy SPS - monti, digi, Birdnest. Then try some standard torts, stag etc. If everything is successful to that point (probably 6months plus) then you can drop some $ on some nice collector SPS with confidence. Remember you can always sell off some of the more common stuff to help make room and to have a little coin to get what you really want.
Along the way you’ll have to start dosing. A tank like that a dosing pump is the easy route. At the start you can even just dose by hand. I did for years. But even a smaller tank full of beautiful acro colonies and frags will go through a serious amount of ALK, Cal, and Mag. I’m a fan of Calcium reactors for long term costs and stability with acros.
Side note. Looks like from the pic the bottom is full of rock rubble. You might find it extremely difficult to maintain. Detritus will be an issue. You’ll want to blast the bottom with flow and leave minimal areas for detritus to collect. It probably still will collect in a corner or something but it will be easy to vacuum out. Even with elevated frag racks it’s hard to stay on top of detritus. Personally I do like having some rock in my frag tank. You can glue down grow-out pieces and distributed frags around it. IMO acros always grow better firmly mounted.