Rather than a big bouquet of flowers once in a while, if you really want to make a girl happy then give her a little bunch of flowers every day.
花束は英語で "bouquet (of flowers)" / "flower bouquet" 又は "bunch of flowers".
"Bouquet" の方は豪華なニュアンスがあります。
「女の子を本当に幸せしたいなら〜、。。。」というように英訳例を作りました〜
"Rather than a big bouquet of flowers once in a while, if you really want to make a girl happy then give her a little bunch of flowers every day."
ご参考になれば幸いです。