You are good

I'm not so much in smoothies. But as I know there are many categories of smoothies: Health, energy, refreshment... Write about changing fruits or adding some spices. I'm sure, if you google 'smoothies recipes', you will get tons of ideas. Write about which smoothies men like more and children are crazy about.
You see Javiera, it's endless.

Talk about and review some of the smoothies out there. I know around Seattle there are a lot of smoothie companies out there review some of them. How do they compare to yours? What do their have in common with yours, or what's different about theirs. Are they filled with sugar and other not so great things or are they healthy, like yours? You may have to go and buy one of their's but that makes the review more genuine and makes you the authority.

Break content down into some specific categories like for weight loss, weight training, stamina, good nutrition etc.

If people are looking to gain bulk, can they do this with a smoothy?
Are there specialty smoothies that increase energy?
History of some of the ingredients might be interesting to many people.

(I am not a partaker of smoothies, but I appreciate the idea!)

Over the years of creating blog posts for clients, one 'trick' I learned is to watch out for FAQ (Frequently Asked Questions). When people ask a particular question frequently, it is a signal that it is a topic that they, and many people like them, want to know. So that makes a good blog post to write.

Another source is to go to Quora and other Q & A sites. Search for topics related to your main topic. You will get plenty of ideas there.

Hope this helps?

Blessings.

P.S. I think I will write a blog post about this. See? Another blog post to be written. Haha :)

Hi Javiera,
Yes a lot of us run into this same challenge. Have you gone back and read the posts you already have, to see if amything new comes to mind?
Google smoothies and see if the internet can give you any ideas.

I have a food blog and I'm having a hard time right now too

Smoothies, I think fruit. U can talk about different kinds of fruit to use, health benefits of different fruits, where fruits come from in the world, how to prepare fruits, where do u get them from, etc. I am going to guess that there are veggie smoothies too? If so u can talk about the same things as the fruits with different veggies. If u put ice cream in a smoothie, then u can talk about how to make your own ice cream or yogurt maybe. Don't know if the last 2 are in smoothies though.
Any of the ingredients can be broken down into informative posts about what they are, where they come from, where do u get them, what makes them healthy for u, etc. Then u have recipes, tools u need to use like knives, spoons, blenders, anything u use to make a smoothie like what are the best tools to use for any given smoothie. If there are smoothie machines then do reviews of the different brands. All things to talk about. I hope this helps a little, I am sorry if it does not, but I do not know much about smoothies besides that they are some kind of health drink I think. What exactly does a smoothie do for the body? U could do a series of medical articles about the different benefits of different kinds of smoothies. Well, cannot think of anything more right now.

Ideas are infinite Javiera and the internet search is full of them!