well what you put in your tank is really up to you and your tank. You mentioned a couple clowns, getting a pair of clowns I think would be a great way to start. (obviously after the cycle has completed
After you've had your clowns for a while, and you're comfortable that your tank is stable you could probably add a tang. The corals should come a bit later and anenomes much much later
that, unfortunetly, is about as close as you'll come to a timeline. everyone's tank is different. their water parameters, lighting, rocks, sandbed etc all affect the overall performance and stability of a tank so the time between each of the steps of your tank can vary greatly from someone else's experiences.