If you've had a few drinks, theres a good chance taking 2ml of g will be a waste of time entirely. Alcohol takes priority in the metabolisation chain, and is broken down first - which takes a few hours. So for this time the g will be waiting for the enzymes to be available to break it down for you - thus negating the effect until far too late. And what often happens is people think the drug isn't working, so they take more, it builds up - and you get a grand mal od a few hours later.
People don't usually sell 1-2ml, they sell 20ml bottles in clubs - commonly the little HDPE bubble bottles from safeway/woolies.
Buying at some kind of rave off dodgy cunts (especially if its the hardstyle scene) you're likely to be buying something thats about 70% tap water... so enjoy paying money for that...
Find a source well before your event - G can't be smelt by snifferdogs, so as long as you're not carrying anything else you should be fine. Be cautious - also i suggest TRYING the drug well before you start taking it at events, so you can be sure of your tollerance and perfect dosage.
My experience with most g was with pure substance, and it can't get any stronger than that - my dosage was about 3ml every 2-3 hours. For a newbie i'd suggest start at 1.5, and redose at an hour or so with another 1ml... that should give you a fairly good effect - if that not enough for you, wait another 2hrs and dose 2ml... increase in .5ml incriments until you find your ideal dosage, and never 'double-dose' in the 2hr period to avoid overdose.