。
She told me which clothes I should wear.
Literal
She [topic-は] me [to-に] which clothes [object-を] wear-go [if-たら] good [question-か] taught [for me-てくれた].
Two compound verbs and two grammar patterns. (1) 着ていく (the te-form chain 着て + 行く) — 'to wear (something) and go,' i.e. 'to put on and head out' — captures the act of dressing for an outing. (2) ~たらよい(か) is the embedded advisory pattern 'should X / what would be good to X,' used with a wh-word (どの服 'which clothes') as a question of guidance. The whole embedded question 'which clothes would be good to wear' is then taught to the speaker.