First of all, I second the recommendation for spring straps. They are literally the best diving invention since sliced bread. They simply remove the fin related klutziness from the diving experience. I know whereof I speak.
Regarding signals. The biggest problem underwater at the beginning is that you are simply at the edge of overload just from being there. If you are anything like me, the minute ANYTHING raises your stress level, your brain just blanks out and sits there. Somebody can make all kinds of gestures or even tap dance in front of you, and nothing comes through. If they write it down on a slate, you look at the slate and it takes forever to read what's on it. You're not narced (unless you're way deeper than I was), you're just maxed out. It gets better.
Part of what helps a lot is when you have enough dives to be able to anticipate what somebody is LIKELY to be communicating to you. I mean, if it is toward the end of the expected dive, you're likely to get signals to communicate the remaining air supply, or to request to go in or up. At the beginning, you may get signals indicating something isn't right and somebody's ears are having trouble, or the like. It's just like understanding what somebody is saying to you in a noisy nightclub -- if you know what they are PROBABLY saying, you can interpret much easier.
One of the really big, troublesome sources of anxiety for me in my early dives was being confused about what was being said to me. Being a violent overachiever, it was not acceptable not to understand, but I didn't understand. By the time somebody dragged the slate out and wrote it down, I was frantic. You have to let go of that.
Complex ideas really can't be communicated underwater by hand signals, although you can do a lot more if the divers are really familiar with one another. That's why carrying a slate or wetnotes is so handy, although the task loading involved in writing something down is a lot for a novice diver
Remember your first riding lessons? Give yourself some beginner space. Getting the rhythm of posting right has to precede straightening the horse. Getting basic buoyancy, relaxed breathing, and efficient propulsion has to precede being a good communicator, as counterintuitive as that may seem. You need enough processing power to interpret signals, and at the beginning, you may not have it.
