セッティングは整えておいたから、後はまーくんが根性見せなきゃダメだからね？

、？

I've got the setup all squared away, so from here on Maa-kun, you've got to show some guts, got it?

Literal

Setting [topic-は] arranged-[in-advance-ておいた] [because-から], afterward [topic-は] Maa-kun [subject-が] guts show [if-not-なきゃ] no-good is [because-から-ね]?

セッティング is the loan 'setting/setup.' 整えておく combines 整える ('to arrange, prepare') with ておく ('do in advance'), yielding 'got X arranged in advance.' 根性を見せる ('to show guts / spirit') is a fixed expression key to the Japanese 'sports-drama' vocabulary of perseverance. なきゃダメ is the ultra-casual contracted form of なければダメ ('have to / must'). ~からね at the end gives friendly, insistent reasoning.