Hi HyperGirl, well, here are a lot of people who have gived a lot of useful tips
I'm using a Wacom Intuos3 A5, it have like 4-5 years old and it was a bit expensive when I bought it but it worth all the money I paid. If you're going to make art as a hobbie you can buy a wacom bamboo, it's not expensive as an Intuos and it's very great even for high works. If you're going to make professional art, first you can start with a tiny Wacom Intuos (like A5).
If you're going to use a mouse, yes, you can, it's a bit difficult to start with tablets but it helps you get better drawing freedom and also it takes less time to complete a drawing. With mouse if you want to have great linearts you can use in photoshop the pen tool, or try with Illustrator. I've drawn for several years with mouse but really I progressed more with a tablet.
I used a tablet once, but the magnetic field it uses is a weak version my hands put out, and makes the tablet useless.
I have never had a problem drawing with a mouse. I am actually very fast at creating art because I don't try doing everything the hard way, just because I an use to doing it that way. I adjust. Digital art works better if you fill and draw, and if you want lines you have to fill shapes first, just to do it quicker for the programs.
I was on the phone with a company that wanted me to draw a scene, but before they started describing it, I asked them to give me a chance to open Photoshop. When I was ready I said start. They described everything they wanted and I drew everything at the same time. There was a little lag time but when they were finished I save and asked them for their email address so I could mail it to them. I couldn't tell if they liked it because they were speechless, but after a while they said they thought I was drawing a sketch not a finished image. I said the finished image is easier than drawing a sketch or a bunch of lines, because the program don't work that way. So they payed me and gave me a WOW rating, because even the simplest things made them say wow for days.