I don't find the net to be all that helpful in team fights or early on unless you're in a position where you can't get pushed away when you use it(ie next to a thick wall) or in a position where your team could pick them off, setting pre-emptive traps is usually has a high success than using the net, since I mostly use the net to catch up or get away and it works perfectly fine at level one.

One thing I forgot to mention before, I don't really find it wise to use manamune since if you just make all of the seals as Mp5/lvl you do not tend to have a problem with mana past level 10 if you're not going all crazy with your skills, the space would be better suited to an item like Last Whisper.

Also I feel that the mastery point you put in AP/lvl would be better suited for the exhaust boost and exhaust to be used in place of Ignite, since Cait's ultimate does just fine at finishing them off.

When I say skill order, I mean which order to get them in, not use them :)
Also, I like to level the net first because it's a skill you can aim and use in a fight more effectively, at least for me that is.

While I see the benefit of maxing Net before the trap, I have found that it is best to max the trap before the net.

About your skill order (R>Q>E>W) I would like to inform you to never ever use Ace in the hole first unless they already have lower than 170 hp(at level 1 ult on another carry)