There are many things you should do:
1. Create as many as you can. Including image, content, video... You will see which one is the best for your product, which one is the most attractive.
2. Change your ad. Normally, one ad can only be affective in 1 week or a bit longer. Changing it gives you more opportunity to reach your ideal audience.
3. Prepare a good product (actually this must be the first thing you must do).
4. Know your enemy, know your partner. Take time to research about your opponents, read all the rules or policies from any forum, social media.
5. Last thing, learn and use the right technique. You can't do thing if you don't learn.