The reply about CTR and bid amount is correct - you have to have a minimum CTR (usually two weeks worth to prove an average) and then a bid jump way above the #1 spot (usually takes around $2 above the #1 spot to get the ad moved over to the top of the natural results)
Also there are some keywords where Google doesnt allow the ads to move over to that spot - so make sure you are going for a spot where youve seen someone over there before
There is no minimum amount spent over time to get there - I used to do it with a budget of under $500 a day so it should be pretty easy once you have the CTR