I always start off by doing at least 5 5-10m circles on each rein in my warmup and that really helps!
You can also do the spiralling and getting you horse to spiral in by putting on your outside leg and spiral out by putting your inside leg on.
Also for the relaxing you could try rescue remedy, I used to give it to my old pony before competing cause he got really stressed on the float and out at comps and it worked! It's made for people though so you could use it.
For bending you can do seprpentine across the arena and even over poles.
You can do a spiral and for the spiral do it both ways and both ways bend in and out of the spiral, itsll feel weird for you and your horse when you bend into it but it helps with bending and loosening up.
Then just go crazy in the arena, do a lot of circles and cut across the arena in weird ways, so some serpentine should and zig zags and go over some ground poles, and go in all directions. Your horse will pretty much just be focusing on bending.
And as for the shows just have fun! And don't think bad things. There's this method called the green monster, every time you worry or think you can't do it your monster gets big, think to your self "we can do this" "we will go great" and those phrases make your "monster" smaller, it sounds crazy but sometimes it really does work.
Just have fun with the show tho and remember that if your tense your horse will sense it and become tense as well.