Welcome aboard, PUR_salt_vettech!
It almost doesn't matter which items you purchase in which order - though, I suppose you _could_ run a reef without a skimmer (keep it lightly stocked!). Your pump, for instance, won't work without the tubing, and without the pump, that tubing is just a siphon. Bring it together, one or a few pieces at a time, until you reach a critical mass ... then begin your build.
Meantime, hang out here a while. Explore. Learn. Ask questions, and learn more. Then, when you've got a glass box filled with moving salt water and lit by rays that simulate the sun in the crystal blue waters just off your shores - share that beauty with us!
~Bruce, who started buying stuff for his latest build back in October - and is still putting things together.