Initially, your account will have a daily quota limit of 10,000 queries per day. You can request an increase in your quota limit by filling out this quota extension form. This process is generally slow and hence if you are planning to market the app, consider filling this form with all the details as early as possible.
On submitting the quota extension request, a member of the YouTube API Services team will manually review the app to verify that all the YouTube Data API guidelines are being followed. Due to this, make sure you're not violating any guidelines by reading our guide on Following The YouTube Data API Guidelines and also going through YouTube's Terms of Service if needed.