I'm looking for some advice... If I don't have a tablet, should I try to use my mouse with the brush tool, or just use the line tool? And is a mouse or a touch pad better?

I've seen animations by people who used the brush tool with their mouse, and they were pretty awesome animations. It's all up to what you're comfortable with. The line tool may be easier, but if you use the brush tool a lot then you could get used to it and become better with it.

Using a mouse would be much easier than using a touch pad. I've animated with my touch pad on vacation, and it was harder than I thought. Most animators like to keep one hand on the keyboard while drawing/editing with the other hand, and it's more difficult to use one hand on a touch pad.

I like the pencil tool. Its easier for me