The phrase "ambitious at first" is correct and usable in written English.
It can be used to describe someone or something that initially shows a strong desire to achieve or succeed, but may not maintain that level of ambition over time.
Example: "The project was ambitious at first, aiming to revolutionize the industry, but it lost momentum as challenges arose."
Alternatives: "initially ambitious" or "eager at the outset".
Her trajectory is marvellously ambitious: at first we believe that she has entered America to leave the past behind her, but then it catches up with her in the shape of her hard-hearted cousin Raisele, who tells Lilian that Lilian's daughter, believed dead, is in fact alive and has been taken to Siberia.
Blocks are easy to make and can be sewn together to form blankets- but don't be too ambitious at first.
Without speed, he believes, you are doomed.Over the past year he has been developing a more ambitious strategy, at first constructed around Chrysler, but now including Opel.
Wilson did not write his series in chronological order (maybe because he didn't have such an ambitious undertaking in mind at first), but Lorna Littleway, who adapted and directed "August Wilson's Women," has sorted them out that way.
Katherine Carlyle is no less accomplished or ambitious, though it could not, at first glance, appear more different from his last, Secrecy, the story of a sculptor in 17th-century Florence.
Other "how-to" poems are at first glance less ambitious.
But as ambitious as that goal may sound at first, when you take a closer look at Shift Labs, it doesn't sound that crazy after all.
A simple idea, and yet so ambitious that it seems almost impossible at first thought.
At first glance, Mr. Ritchie's ambitious paintings, drawings and installations seem to illustrate an impenetrable personal cosmology.
Others pointed out that peacebuilding was quite ambitious at this point in time (second intifada), and that progress was being made in building cooperation among Israeli, Jordanian and Palestinian colleagues.
On the O'Hare project, after resisting at first, Mr. Daley ultimately pushed a far more ambitious plan than Mr. Crown and others had proposed.
