To put your best foot forward means to embark on an undertaking with as much speed, effort, and determination as possible, but in this context the speaker is telling the candidate not to bother trying too hard.
Consider the statement "The grove only takes the top thirty drama candidates from the two thousand who will be auditioning over the next few days, so don't bother trying too hard and just do the bare minimum.". Based on this "The grove only takes the top thirty drama candidates from the two thousand who will be auditioning over the next few days, so put your best foot forward." a true statement? Yes, no, or I don't know?