I've heard a variety of things regarding this. It's my understanding that dubia roachs can replace crickets as a staple. However, IMO, you do want to give your chameleon the biggest variesty possibly and not so much look at it as "which staple(s) to feed".
Also IMO, I think this is something for your chameleon, not the forums (lol hear me out here...) when you get your chameleon, you do not know how he will react and what he will want. He may prefer dubias. Or crickets. He might not want either right away and choose other things. And I think the truly best plan of action for you, is to round up as many feeders as you know you can get regularly, get them all set up, introduce them appropriately, and see what your chameleon decides.
For example, my panthers favorite was silkworms with his breeder. He also ate crickets and what not but that was his favorite thing. When I got him, he ate them no problem for a few days. Once the BSFL came into play, he completely stopped eating silks. Only ate crickets, and BSFL. I also introduced superworms, and dubias. He completely turned both down. My panther was really just eating crickets and BSFL for weeks. I had an idea of drastically downsizing his silks and sticking a few in his BSFL dish, to see if he would either just go for them, or "accidentally" eat them with his BSFL.
The result of that is, he began eating them, what appeared to be "accidentally". Then he started eating them on his own by choice (clearly). And now, not only is he eating them by choice, I put an extra one in there (was 2, now 3) and he's eating all of them AND they're getting bigger and he's still eating them, plus about half a dozen or so BSFL, and anywhere from 6-18+ crickets, depending on the day.
Sorry for the ridiculously long post. However, my point here is that, your chameleon will have his own personality and make his own little decisions. Be prepared for as much as you can, and see where your chameleon takes you
Please keep in mind that I'm a new keeper myself, I am only on my 2nd chameleon. Take my opinion with a grain of salt, and hopefully a more experienced keeper can assist you better soon! Best of luck!! Please share pictures :-D