Are any of you actually knowledgeable in computers?

I need to get me a computer for school cuz sharing this one with my husband just isn't working for me.

So, I need a computer to do Online courses, keep track of my quiver biz, personal finance, and just random other stuff like picture storage and recipe files.

What do I look for?
What brand would you recommend? Dell, Lenovo, HP, Toshiba, other?
I am looking to spend $500-800 max.
I prefer to have the number key pad on the side since I will be using it for Math classes alot.
My kids might watch the occasional movie when we are traveling, maybe.

Thanks!