When you say that you design clothing sketches its very important to know whether your are a professional who are doing this, or a fresher. Also what kind of professional training you have had!
Because when you express your interest in having your own clothes line it depends on factors like number of years of experience,expertise etc.
In terms of courses you can consider courses like fashion merchandising or retail management which will add a business perspective to your knowledge of fashion and clothing.
By pursuing courses like these, you can consider working with ready made cloths company, retailers,chain stores,export fabrication companies and export houses.You can also work with fashion designer to bring in new Products And after substantial experience you can have you own clothing line.
Hope this helps.
Kindly revert back for more queries and clarifications.