You could start with the SE bundle wich you can upgrade to some point. I'm also still waiting to make my first purchases.
I would start immediately with the dvd libraries or the download instruments. The download instruments are a bit more expensive,
because you get a license for each instrument instead one license for a whole collection, but this way you can upgrade each instrument,
independently wich is not the case with the dvd libraries. Both dvd and download collections feature the full samples collections.
Only the strings are not available as a download instrument. If you want a very realistic sound you should get vienna MIR, I demoed it with the special exploration kit and I wouldn't buy any collections without it. To get most out of you library you should get vienna instruments pro.
My advise: start small instrumentwise (downloadinstruments or full dvd) but buy vienna mir with it. Mir requiers Vienna ensemble pro.
There is a special bundle offering these two softwares with a discount, you should check it out. Please mind that if you do start with the SE bundle, you can buy the full dvd libraries or downloadinstruments later with some discount.