ただ、毎日だとさすがに飽きるだろう。もっと料理のバリエーションを増やさないと。

、。。

Still, if it's every single day, you'd get sick of it even so. I'll have to expand my cooking repertoire.

Literal

Just, every-day [if-だと] as-expected get-tired probably. More cooking [gen-の] variation [obj-を] must-increase-[if-not-ないと].

ただ at the sentence start is a discourse connective 'still, however, just.' だと is the casual equivalent of のだと or であれば — a conditional expressing 'if it's X.' さすがに ('as expected / even so') acknowledges that while the speaker wouldn't normally mind, under this condition they would. バリエーション is the loan 'variation.' ~ないと is the truncated 'have to' again. The whole line is a self-addressed resolution.