My daughter competes at pre-pre and her dresses are pretty blinged. I sew them so we have a great time designing together, it is part of the fun. I also make dresses for other girls at the rink and on average, I'm using 3-5 gross of stones with a dozen or so larger sew-on crystals. For a girl skating at the later basic and beginning freestyle levels, it tends to be fewer, maybe 1-2 gross of stones. I think this can vary regionally, parents take skating pretty seriously where I live.
I know girls who wear the same dress for all events and I also know girls who wear two dresses - one for freestyle and a basic dress for other events.
As for practice ice, if the rink isn't too far away, we have found that going for a freestyle session during the week before helps ease anxiety over skating at a new place. My daughter loves competitions but she also likes to know what she is walking into and that helps her arrive on the big day feeling at ease. Practice ice is stressful to me because it adds another time you have to pay attention to during a fairly loud and busy day. I get the most stressed out about time since my family has a tendency to wander in all directions - we're an ADHD family, literally. That is my least favorite part, I ALWAYS worry that I won't be able to find anybody when it is time for her to skate.
Good luck, and have fun! It is an adventure.