Generally it sounds good and not to complicated. Here are a few minor suggestions:
plants --you can't go wrong with pothos. It's hardy, grows quickly in a variety of conditions and looks nice.
Crested geckos do tend to kind of stomp on things, so anything fragile will probably not last. Also, I get one of those fake vines they sell at pet stores, twist it up and around so the plants have something to climb up and the gecko has something more solid than the plants to sit on.
Substrate: I'd recommend using something like sphagnum moss as the top layer to avoid possible ingestion of the cypress mulch. The gecko poo will make its way into the soil and fertilize the plants and the--
Isopods: I have used roly ploys from the great outdoors with no problem. Some people prefer to collect them and keep them separately until they've reproduced and then put the new generation (which hasn't been outdoors) in the cages, but I haven't had any trouble with using them directly. About 5 years ago I bought a container of white isopods and a container of orange isopods at a reptile show for about $10 each. I move some of them to each new enclosure I set up. Five years later, I still have descendants of the same isopods (primarily the white ones) in about 8 enclosures.