There is never a “correct” amount that you should spend on marketing. However, due to the nature of the platform, you should at least spend a minimum of $1,000/month on Google or Facebook Ads.

The next thing is the industry you are in. Certain industries cost more per traffic than other industries. Usually, it is because their average customer is more valuable. Consult a PPC professional to get an estimate on how much you should spend on your marketing. Don’t spend what you are not comfortable with!