QIAGEN Gel Extraction problem?

Hello I am trying to perform molecular cloning. Problem is, I am getting few colonies on my LB plate (I am using XL 1 competent cells). I thought that my main problem is that my DNA yield prior to ligation and transformation steps is too low (> 1 ng/ul). I measure DNA concentration using nanodrop after each step. After the first PCR reaction my DNA yield is around 500ng/ul. But after agarose electrophoresis and gel extraction I get only about 3 ng/ul DNA at most. I am Using QIAGEN extraction kit. I am following the instructions closely. I also perform ETOH precipitation of my DNA after PCR and after Gel Extraction. What could be the problem? Any advice or tips to improve my DNA yield using this extraction kit? Any help will be appreciated

thank you