If I understand what you're saying correctly, you seem to be mistaken. You don't go to the store and say "I want to buy this item, I put it in my cart and put my card info in and buy it" (like Amazon or something).
Instead, you "donate" the $10 and receive coins (11 I think? It'll tell you), then you use those coins to purchase an item in the store. It's the act of DONATING that gives you VIP status and queue skip.
So, no you don't need to wait until the server launches to buy something from the store to get VIP status, because that's not how it works. Simply donate (through My Account > Donate) and your account will be VIP status (no matter what server you play on). Then, if you fancy something from the store, you can use the coins to buy it.