おい、いい加減パンツネタはやめとけよな、読者が退く、ドンビキ。

、、、。

Hey, seriously, stop it with the underwear jokes already. The readers are going to be turned off — totally creeped out.

Literal

Hey, moderately panties-material [topic-は] stop [emph-よな], readers [subj-が] pull-back, total-cringe.

パンツネタ 'underwear material/jokes' uses ネタ (material/joke fodder). いい加減 'moderately / enough already' expresses exasperation. 退く (ひく) 'to pull back / be turned off' is modern slang for cringing. ドンビキ is the intensified form — ドン (emphatic) + 引き — 'total cringe.' やめとけ is the casual contraction of やめておけ.