I'd add the firefish next, then the angel, and the clowns last. Give your tank 6 months before you add anything like sea stars, clams, etc. Also, give your tank at least two weeks between any additions to allow the biofiltration to catch up with the additional load.
Alrtho your tank is cycled, it's not MATURE, which also means it's not super stable yet. To be honest, once a SW tank is mature and established, they're pretty solid, meaning your parameters won't bounce around or change. Eventually, you'll learn to recognize when to test your water, perform various tasks, etc.
Oh...if your tank isn't covered, do so...firefish are bad about jumping, but ANY fish can, and will jump...including bottom dwellers, lionfish, etc.