精々(せいぜい)at the most, at best, to the utmost, as much (far) as possible

その商品(しょうひん)なら高(たか)くても精々(せいぜい)一(いち)万(まん)円(えん)くらいだろう。

That product would at most cost around 10,000 yen, even if it's expensive.

病気(びょうき)だと聞(き)きました。精々(せいぜい)休養(きゅうよう)を取(と)ってください。

I heard you're sick. Please take as much good rest as you can.

店(みせ)の店主(てんしゅ)：「精々(せいぜい)おまけしますので、ぜひうちで購入(こうにゅう)して下(くだ)さい！」

Store owner: 'I'll give you as much as I can extra, so please consider purchasing it from us!'

病(や)み上(あ)がりなので歩(ある)いて五(ご)分(ふん)の近所(きんじょ)のスーパーまで歩(ある)くのが精々(せいぜい)だ。

Since I'm still recovering from illness, I can only manage to walk to the nearby supermarket within a five-minute distance, at most.

いくらここが離島(りとう)だとはいえ、頼(たの)んだ商品(しょうひん)は遅(おそ)くても精々(せいぜい)３日(みっか)程(ほど)で届(とど)くでしょう。

Even though this is a remote island, the ordered product should arrive within three days at most.