The first time I flew in a box, I looked down at the white markers, and it looked about the side of a postage stamp!Most of us don't have the luxury of competing in a box that we are familiar with, which is a BIG advantage in staying oriented. You may not even be aware of it, but you will rely on familiar landmarks around your home box to orient yourself at the very high altitudes that competition aerobatics is flown at for safety reasons.
If I had one tactical piece of advice to someone starting out in competition aerobatics, it would be this:
Don't be afraid to take a break!
Breaks are so cheap, points-wise, in the lower categories, that you are foolish to push the boundaries of the box (or a slow airspeed) and end up flying a maneuver worse than you could if you restarted at the right airspeed in the right place.
Depending upon who shows up, you can take one or even two breaks and still win your category, not that it really matters.
Hopefully you are lucky enough to have some experienced aerobatic pilots nearby who can teach you this kind of stuff.
You have a huge advantage with a 2-seat aircraft. Most people flew single-seat aircraft and were usually self-taught. The lucky ones found someone to critique them from the ground (short after, etc). Note that someone who judges/critiques you from the ground will simply tell you what they saw, and usually it's up to you to figure out how to fix what's wrong. With a 2-seat, you can have an experienced aerobatic competition pilot ride along and show you how to do it correctly, at least according to the IAC "Red Book", which I would recommend getting for any pilot thinking of competing.
Remember that all of this is worth precisely what you paid me for it