This would be my advice as well. I agree with all that have said that importing Gedcoms often create a mess, and that is why you should start by adding smaller gedcoms, 50 persons seem a good number.
I still have a lot of cleaning up to do of some imports 1½ years ago, but I still find it easier to create small gedcoms when I have a new family to add, In my genealogy program, i can add sources and they are tranferred fine to Wikitree, but there is some editing to do in order to make it look all right.