When people come here, ans say they have been lurking, I always wonder if they really have been. And then some people make a comprehensive list of their plan, ideas, so on, and it is evident they have been, and are genuinely interested.
So I can whole heartedly say welcome, we are glad to have you.
I once did a LOT of changes, and noticed a huge change, so now I try to do one change at a time. But that is me, I like to know exactly what is going on. I just finally did a speed chart to see my stats, so I will know what my changes are doing.
But if you get those changes done, you should see huge results. I PERSONALLY would do the airdam first, then rear wheel skirts. Then, instead of building the wiper thing, I would just put them in your car for the trip, maybe get some rain x. And a friend of mine here noted that his wheel covers did nothing for him. He did extensive testing. Please note that this does not mean they do not work, rather they might not make a calculatable change over your current rims.
But your plan sounds good, I look forward to reading the results.
EDIT:
I just saw your join date, CLEARLY you have been lurking for a while lol