I have both and they both a a place to use them. The Spark is great if you just need 10-15 minutes of 1080/30p filming that doesn't need to go a long distance. Anything else 1080/60p, 4k, far distances, or longer flying times you'll want to use the Mavic. They both use the same app and if you have the controller with the Spark it is very similar to the Mavic's.
Regardless if it is your first drone they will both be a great drone.