I am sure most people at some point in their life think about writing their own book.

I am trying to get ideas to write my first book, so I would really apprieciate to hear what topics u had thought to write about - or if u have any ideas that aren't too precious to you and u would like to share?

I am open to most genres

you write about what you want to write about.
and write what you know.

Honestly, if you have to ask others what you should write about, you have no business writing.

Try free writing for a little. Just sit down at a computer or at a desk with some paper and a writing utensil and let your thoughts flow.

This.

Although what is more important is the actual ability to write. If you have the most unique and exciting idea in the world, but have no talent at writing, then your book will be shit. It takes a lot of time and effort to write a book. Of all those people who actually think about it, it's a very slight percentage that actually get published. And what is the point of starting to write a book if you don't plan on getting published?

If you do actually put the effort in, I wish you the best of luck

Yeah I think u should start some free writing or some sort of writing exercise, that in itself will give u some ideas, as well as giving u ability and practice. Taking your time to read some writing tutorials would be a good help as well. You can also start writing a journal, or write about your dreams which is a never-ending source of material. Just throwing some ideas for you, let me know what works out best for you.