"One does not grow up dreaming of being a mayor's wife," mused Effi Barry, who will become a mayor's wife tomorrow at the inauguration of Marion Barry.

"There is a vast amount of responsibility in a position like that," said the willowy Mrs. Barry, who has already served a long apprenticeship as a political wife. "It's not all glamor. It involves a tremendous personal sacrifice in terms of time, energy and the loss of privacy. I only hope I can perform in a manner becoming to a representative of such a fine city."

That was before she went to stand in a receiving line for an hour, and then to speak a few words (which amounted basically to "thank you") at a cocktail-buffet reception given for her yesterday evening at the home of Mr. and Mrs. John Stewart III. Approximately 200 guests, mostly friends of the Barrys or members of the city government, but including a sprinkling of diplomats and many young black professionals, gathered for a quiet tribute to the city's new first lady. Enthusiasm was high among the clearly partisan guests, both for Mrs. Barry as a person and for the new dynamism expected of her husband's administration.

"What a fine, stately, fragile-looking first lady we have," said one woman guest. "She reminds me a little bit of Jackie Kennedy," answered another.

In the last relatively quiet days before the inauguration, anticipation was both strong and varied on what can be expected of Mrs. Barry in the next four years. "She is very interested in the diplomatic community and in education," said George H. Sealey Jr. of the State Department's Office of Protocol. "I expect to see her finding ways to use the tremendous resources represented by the foreign embassies in this city -- to bring the Washington community and the diplomatic community closer together."

Her husband, introducing her to the assembled guests, was less specific but equally enthusiastic: "She has some ideas of her own, and we have talked a great deal about what she is going to do and about what I am going to do. You may be sure she is not going to just sit around watching."

Mrs. Barry herself was reluctant to make any predictions at this early stage. "I see many things that need to be done in supplying a new life, growth, heart and a new feeling in this city," she said, "but I think there should be a period of consideration before I say more. I certainly don't intend to waste my time on ceremonial things that don't have any effect. But anything I do will be in terms of being I do will be in terms of being supportive for my husband's efforts." CAPTION: Picture, Polly Harris, Norma Stewart, Mattie Cummings, Margaret Stewart and Effi Barry, right, at last night's reception, by James M. Thresher -- The Washington Post.