“You’re a really good waitress” is a compliment no 27-year-old college graduate wants to hear. So in writer-director Noah Baumbach’s Frances Ha, the title character (Greta Gerwig) immediately and realistically responds with, “I’m not a waitress,” though the fact is that she needed to take this private-event gig—at her alma mater, to make matters worse—because the Brooklyn resident has no other prospects to make quick money.

Even calling Frances a “resident” of anywhere is stretching the truth. At the beginning of the black-and-white film, she’s living with her best friend, Sophie (Mickey Sumner), and turns down her boyfriend’s proposal that they move in together because she doesn’t want to leave her roommate. Sophie isn’t so sentimental, though (even if the two share the kind of affectionate bond more characteristic of lovers), and soon moves out. So Frances hops from apartment to apartment, crashing on couches and leaving when she’s too broke to help pay rent.

Frances Ha is a departure for Baumbach (The Squid and the Whale, Margot at the Wedding, the intolerably bitter Greenberg), who here shares screenwriting credit with his star. Frances may be a millennial mess (“I’m not a real person yet,” she tells a date when she insists on paying but realizes she has no cash or viable credit cards), apprenticing at a dance company even though she has no chance of officially joining, and feeling aimless in general. She tells rambling stories and lies about her professional opportunities, and she has a sense of humor no one understands. One temporary male roommate deems her “undateable.”

Yet none of this seems to make Frances self-conscious; she cheerfully and repeatedly puts her unformed self out there and tries to ignore weird looks or any development that upsets her. There are fleeting instances of Baumbach’s trademark angst, but you have to look hard to see them. It’s Gerwig’s most enjoyable and uplifting performance yet, likely because the material seems so suited to her: Frances may have nothing, yet she runs and spins down city streets, scenes that Baumbach shoots from slightly above so the camera seems to lose its breath to keep up with her. Her moments of sadness are quickly smothered by her strenuous optimism, even if you’re not sure what drives it beyond the joy of being young and free in New York. The script’s humor is quite dry—examples wouldn’t read like jokes at all—and the film’s tone purely exuberant. Frances’ friends may be growing up, but it’s her lighthearted, childlike attitude you end up envying.