Usually my main problem is that I don't think my Pok?mon have usable moves. Any tips? Condition is no problem but moves... well, I usually run two moves that raise the attention of the condition I'm playing, a neighbor move that does not raises attention and finally a move that lowers it.
Usually, you don't have to worry too much about how to win. Most of the time, if your Pok?mon has max condition, there isn't too much to do to get first place. I ran a lot of different movesets, but all with a mandatory standard move (4 hearts) and other available stuff, either to prevent damage or to enhance confidence. I never really worried about the ovation.
Also, remember there are combo moves, like Defense Curl + Rollout or Clam Mind + Stored Power that really help getting chunks of points while being good in the contests. My Gardevoir kept spamming Calm Mind + Stored Power and won pretty easily.
You also get bonus hearts if your Pok?mon mega-evolve in the contest.
Do you have exotic Pok?mo? This is tiring but you can trade items via GTS, like for example, you upload a Zigzagon requesting a Xerneas. Then on X/Y you trade said Zigzagon with the Xerneas holding the item.
I will have to resort to that if I don't find anybody with a Japanese 3DS. I grinded those items so much that doing it again already tires me.
Especially those Leftovers.