one thing about the word "should" -
there are a million different ways to run a successful, wonderful system. What works for one person may not work for someone else, and what is "pretty" to one person may not be so nice in the eyes of another. You have so many options!
My suggestion is to keep in mind what your end goal is, with the understanding that it may very well change as you go! What fish do you want? What kind of corals do you want to keep? The answers to these questions and more will help you decide what lights to run, what pumps to get, how deep your sand bed, how much live rock and what the formation the aquascaping might be, how much flow you need....
The one thing you should do is read a ton. Look at tank threads and see what others have done. Ask members whose tanks you really like about the way they did their set-ups (that's what I found most useful). There are some great books out there, but on this site alone you'll find so much info from helpful reefers.
That said, I would not pay a lot of money for one really good pump with the intention of buying an even more expensive, better pump soon after. I'd want to start with the best if I could afford it. But that's just me. I'd rather do without while I save for the one I really want.
In terms of when to add corals and fish - wait till your cycle is complete. What fish you add and the order in which you add them will depend on the fish you want and their needs. If you want fish that eat the tiny animals that live on the live rock, you will need to wait quite some time for the tank to really establish itself. Specifically, I would not add a mandarin or a six-line wrasse or any of those "pod-eaters" for six months at least, maybe a year or more. Frankly, I won't add them at all for fear that they'll starve in my system, but I'm particularly averse to fish dying in my tank
When you are ready to buy fish, make sure you get ones that are healthy and eating prepared foods already!
You can add corals whenever, once your system is stable and mature, but go slowly (the very hardest part!)