You're right, I should have done that from the beginning.
That would have been better, wouldn't it?
この場合、次のような言い方ができます。
ーYou're right, I should have done that from the beginning.
「本当だ、最初からそうすればよかった」
ーThat would have been better, wouldn't it?
「その方が良かったよね」
ご参考まで！
カナダ 
