Even though I suppose you already know this: each piece of gear has a certain cap on each stat - so theres your first cap.

To give you some general advice: Never get more of any stat than you need to craft the highste tier of gear available at that very moment - most of the time thats gonna be around the stats that you have to reach in order to be technically able to craft said gear. As soon as you can more or less save craft that gear and have a good rotation for it, there is little to gain from increasing craft&control (CP might be something we can discuss...). When melding it might be a good idea to leave slots open to enhance your gear as soon as you need it - aka when a new patch hits