If you understand the logic behind scales, then you would need to worry about how many scales to learn, you learn one.. know the logic.. there is no count of how much you will be knowing. Yes.. but about how much thorough u need to become with scales is.. i must say yes.. practice an much as u can.. it will be very useful when u move further to chords. Here is a link for you:

http://learnplayingguitar.blogspot.com/2011/09/understanding-guitar-scales-and-how-its.html