When getting Botox for the first time, would it be better to try it on just one area?

I started worrying about my forehead and the space between my eyebrows together.
I'm considering doing both areas at once.

However, since it was my first time getting Botox,
I'm also worried that my expression might be different from what I expected.

At first, try just one area that you are most concerned about.
Would it be better to check how the changes occur on my face first, and then decide on other areas?