Stick with the beginner putter,and try aiming differently,and lengthening or shortening your putts,rather than doing the same thing each time.If it doesnt work the first time,it will not work the second time either.
Save your money for a new outfit or some decent balls,but dont waste it on an expensive putter that does not and will not correct your own ability to change.
I'm saying this from my own experiences with equipment,and my own inability to take the leap and change what I do to make every putt count.Others will slap me down,but they will not change my opinion on the attributes of the expensive putters against the free one,and a willingness to adapt to methods that will negate any perceived benefit from financial outlay.Believe to succeed.