I already have giant steps / huge strides
in the context of
‘Having previously taken tentative, half-hearted baby-steps Sophia began taking ——– towards attaining her life’s ambitions’.
See Cambridge Dictionary online for examples of usage in this context, generally by British parliamentarians, e.g.
”Is this not a giant stride towards a nationwide capital-owning
This to me is the most natural opposite to “baby steps”. “Strides” seems to me more idiomatic than the “leaps” suggested in another answer. Certainly a comparison of the terms using the Google ngram viewershows “giant strides” to have a longer history of usage, and even today is much more common.
A stride is a large step, whereas a leap entails taking both feet off the ground and often has the implication of jumping over something. The idiom here is “leaps and bounds”. To use this I would recast the sentence a little:
“Sophia began moving towards attaining her life’s ambitions in leaps and