誘ってもらって嬉しいけど、この次にしておくよ。

、。

Thanks for asking, but I'll take a raincheck.

Literal

Invite-[receive-てもらって] happy-but, this next time [on-に] do-[preparatory-おく]-[sentence-final-よ].

A polite decline. 誘ってもらって ('having been invited, inviting [me]') uses ~てもらう to cast the invitation as a favor received. 次にしておく ('make it next time, save it for next') uses the 'decide on X' ~にする plus the preparatory ~ておく — literally 'prepare to make it next time.' A graceful, warm refusal worth memorizing.