Many forum members have already given informative suggestions or answers on this topic, hope they will be helpful to you. Still some tips from my side, there are several things you can try to improve their performance:
Optimize your gig's title and description
Use eye-catching images
Offer competitive pricing
Promote your gig
Improve your gig's SEO
Analyze your competition
Create multiple gigs on the different category
Use videos on the gig
Optimize your gig's delivery time
If needed keep your gig's description up-to-date
Attend Events and Conferences