Hi CTL!
Manolos are an investment. Aside from purses, I have a large closet of shoes, with Manolos making up about 1/3 of it. For comfort when it comes to high heels, nothing beats a pair of Manolos.
I would definitely advise you to go to the boutique to try the shoes on. Manolos are consistent in sizing but if you're completely foreign to the european shoe sizing, it would be a mistake to order online.
$700 is plenty to spend on a pair of Manolos, though if it's your first pair, I would suggest something a little flirty but classic, like these:
Have fun shopping!