Change up, I agree.
A good change up is a beautiful thing.
Take some time with it. Get comfortable with the grip. Play catch mixing in the change up grip. It takes some time to get comfortable with it, but, it is worth the investment.
Once you get comfortable enough with it I would recommend video yourself throwing the pitch off a mound. Does your arm slow down noticeably? Does your body or motion slow down? A lot of times these things happen without the pitcher knowing it. Because they are thinking "slower speed", everything slows down. Not only does this make the pitch less effective it can tip the pitch to attentive hitters/coaches. Remember, a change up is a pitch that is supposed to draw swings. It is meant to be thrown for strikes, so, it has to be deceptive enough the hitter sees a meaty fastball center of the plate. Throw a set of pitches, watch the video and adjust. If you are able to gun the pitch as well this helps. Getting a good spread in the pitch speeds, 10 mph or so between the FB and Change up is what you will be looking for. Also, as you advance with the pitch, if you film some from behind you should be able to get a good idea of movement. A change up which is deceptive and a good amount slower than the FB is a very good pitch, add in some late movement and it can be a knock out pitch. I have been fortune enough to be right behind the catcher (not an umpire) while Clayton Kershaw was working a session several years ago. All his pitches were impressive obviously. His curveball gets a lot of attention, but, from down there that change up was something else.
Good luck with it. No matter what changes in baseball somethings stay constant. One of those in my opinion is FB/Change is the best combo in baseball.