I've always been a fan of dragons and dinosaurs, so when I saw the type effectiveness of dragon-types, I made that my primary focus. My teams usually looks along the lines of my starter (usually fire-type) (to counter Ice weakness) Aggron (to counter both Ice and Dragon) one fully evolved Dragon-Type (usually the most common one I can find), one legendary (usually also Dragon-Type), and one other pokemon that I caught early on and I trained to work against most of its weaknesses. Of course, these pokemon can also counter their own weaknesses, but it's always good to cover your bases, especially with dragons.