How do you get more gummies in ameba pico?

You can always get props from other people and play games. Another way you can earn gummies is to eat food or serve food, but you have to be home, when serving, in order to get the gummies. Another way if you are really desperate is to somehow complete tasks in your star book and earn gummies that way. At first tasks in the star book are easy but then they get harder and require a time machine. When you first join, and finish the tutorial, you are given 5 tokens.
You should use 1 of those tokens to buy a time machine. Or, if you already used them all, finish the daily scratch card to get a token, or sometimes, if you're lucky you can win one on the Daily Gacha.

If you are stuck on a star, you can always google 'how to get stars on ameba pico.'