has anyone had experience with higher gain dbi antenna's for wifi?

i bought a 7dbi antenna to replace the 2dbi antenna that came with my wifi pci card on my desktop and it didnt help at all, it actually made the signal strength and connection a little worse, or you could say, more laggy. are these things supposed to just help in very specific ways, or could it also be that maybe the antenna im using, isnt applicable for the wifi card, or just cheap in quality? i bought it for like 4 dollars on ebay. so do these things help really? if so, in what ways, because this one i bought did not help in any way shape or form. like i said, it had just made my connection worse. what would be a good solution to improve the signal strength / internet connection quality and performance besides this, if the antenna thing isnt a reliable or applicable solution? could it be that the wifi card i have just cant supply much power and the design makes it so that the performance can only be up to a certain point? btw, i believe i have the latest driver for the wifi card too, dated 11/25/13.

here is the wifi card i have - http://www.encore-usa.com/us/product/ENLWI-N3

here is the antenna i got - http://www.ebay.com/itm/261072938742?ssPageName=ST...