Parking does not give you good earning unless you've large number of domains. I think it is better if you create pages and set up adsense.

You can earn more money by parking domains only if your parked domain has a very good traffic. If your parked domain currently has very less traffic, then you can not earn more. Because, unfortunately, parking programs do not allow marketing of the domain that is parked.

You can not advertise it using spamming, Can not place links, can not do search marketing, etc.

You can only place the link with the title "Domain For Sale". This is the only allowed thing to market the parked domain.