It really depends on what you want to do with the horse. Personally I would show up around 7 so I could clean my horse up and lunge her and walk her around the grounds to get used to them.
I would get there 7:30 because you need to help out with the horses and you can't get used to the show grounds
An hour before your due to ride
At least an hour before your ride time, but aim for more time than that! You need time to unload, set up water/feed, register, change, tack up, find your ring and warm up before you're called.
I ussually get there 2 hours earlier
I get there when it starts!! It lets me relax and my horse relax!! Also you can hang out with friends, watch others, and be on time.
Get there early enough for u to warm up and get ready. And let ur horse out for a graze and walk