An Elk Grove teen-ager insists that he wants to enter a local beauty pageant and vows to wage a legal battle against the Chamber of Commerce, which has refused to let him compete. Jason Gaskins, 18, said he decided last month to become the first male contestant in the 29th annual Miss Elk Grove Contest, set for March 27. The contest, sponsored by the Elk Grove Chamber of Commerce, drew 14 applicants. Gaskins said the chamber initially allowed him to participate and attend meetings where contestants learned how to walk, dress and give a speech. But at a meeting early last week, chamber President Carl Amundson told Gaskins the contest was for girls only.