僕は、初めてサーカスというものに連れていってもらった。

、。

For the first time, I was taken to what's called a 'circus.'

Literal

I [topic-は], for-the-first-time circus [quotative-という] thing [to-に] was-taken [favor-もらった].

サーカスというもの literally 'a thing called a circus' — the という+もの construction signals the concept is being named and introduced, as though the speaker (possibly a child) is encountering it for the first time. 連れて行ってもらう is the passive-receiving form: subject was taken (by someone kind), with もらう carrying the gratitude.