I don't like to use those, myself... It's a good starting place, but overall you're probably better off creating yours from scratch. Those are good for patterns, ratios, proportions, maybe... But the quality on some was lacking when I started out so I just made my own and I think that's ultimately what you want to do. Considering you're just starting, I wouldn't totally discourage you from using those... I just won't suggest you use them on every skin.