Question: I have like five different ideas for books and in all of them my main character is a girl and their personalities are a little different but it seems like they all have very similar personalities. Is that ok or would I have to fix that?Answer:
It's not uncommon for writers of popular fiction to create similar main characters for different stories. Perhaps that is because some writers have a hard time putting themselves in the shoes of anyone but a close version of themselves or someone they know. Also, if it turns out the first character is popular among readers, it's often profitable to continue with that type of character, if not the same character.
In the same manner, some writers make a career of writing very similar stories. Most of Lucy Maude Montgomery's books, for example, bear strong similarities to her big hit, Anne of Greene Gables
There can be pressure and rewards from publishers as well as readers to write "more of the same."
However, the practice does smack a little of laziness. It can be more interesting to create characters whose unique traits fit different types of plots. If your first character isn't well received, you also may feel pressured to try something different.
Let's remember too that you may eventually get bored with writing similar characters and want to try on some new voices. JK Rowling, for example, after spending a decade or so writing the Harry Potter series, chose not to make her next book another YA fantasy. Instead, she moved on to adult books and murder mysteries.
All artists benefit from venturing into new territory, and you may find yourself doing the same.
Also bear in mind that the important thing is to publish one book first. Until then, it doesn't really matter what other ideas you have up your sleeve.