Should I sell low value items?

If you sell them, you get back half the coins that you paid, but you'll lose all their Flower value. Be careful not to lose more Flowers than you will be replacing them with, or else you will be in worse Flower debt (AKA "Flower Jail"). The advantage is you'll gain coins to help you buy a high-Flower item to replace them.

Instead, some players place them in storage where Flower value is only lost temporarily; get their Flower value back when you put them back on the island.