Get a desktop genealogy program. There are several for the PC with cost typically about $40; the are fewer options for the Mac, but there are some.
These normally give you the option of starting with a person of your choice and creating a gedcom with ancestors or descendants of that person with as many generations as you want.
There are differences in how most programs handle gedcom data fields as compared to WikiTree. For example, most desktop programs do not have a middle name field, whereas WikiTree does. Most software allows double dates, or date ranges, WikiTree does not. Most software has fields for baptism and burial, WikiTree does not.