“I didn’t see where it states how much Vitamin D you’re supposed to take.”
If you look at various multivitamin bottle labels, you’ll see contents of somewhere between 400 and 800 units, 600 being 150% of reco daily use. I have heard claims that between 20 and 60 minutes in the sun can generate between 5000 and 15000 units. Which is quasi-unbelievable to me, but I am not a biochemist nor a nutritionist so I don’t know. Point being, the vitamin D3 advocates say that type of level (5000+) is what’s called for.
I bought some of this a short while ago, this was about the cheapest source I found, FWIW.
http://www.iherb.com/Vitamin-D
http://www.swansonvitamins.com/Search?doSearch=true&keyword=Vitamin+D
Cheapest place I have found for all spplements.