As you walk around, you’ll notice sparkling environmental items just about everywhere. You have an inventory limit of 10,000, so just pick up everything you can. Flowers, food ingredients, and other items that might seem useless will be useful down the line to craft into various foods and power-ups for your characters.
Flowers and some other ascension materials only respawn after a certain number of real life days, so you don’t want to be in a situation where you have to wait real time to upgrade your characters.