I was thrust into diaper-making when DS was a month old and suddenly allergic to disposables. I also had very minimal sewing ability (I knew how to sew a straight line!), but was able to teach myself to sew fitteds from the tutorials/instructions at
www.diapersewing.com. She gives step-by-step directions with pictures for each step, and it was very helpful for me.
As far as materials, I started out making diapers from old towels. Based on my experience with that, I'd say to stay away from terrycloth. Not because it's hard to sew or anything, but b/c it makes a HUGE mess!
Fleece is very easy to sew into covers, and so rewarding b/c they're so cute

I remember when I made my first fleece cover (it was a really cute bear pattern) I was so proud of myself

Flannel is really easy to sew into diapers. It's what I make my diapers from. And they're so soft, they're really nice. They do tend to fade/pill, but they're the actual diaper part that goes under a cover, so I guess that doesn't really bother me.
Recycled wool is another very easy material to work with, and it's very affordable, too! It's a great way to have the "luxury" of wool covers at way less cost (I get sweaters for an average of $4-5, and can get 2 covers and a pair of longies from each men's XL sweater).
To make a pattern, just trace a diaper you already have (even tracing a sposie will work). Or, if you're feeling daring, the same website I linked to above also has a Diaper Measurements page, and you can use those measurements to make your own pattern from. That's sort of what I did, I just laid out a piece of scrap fabric, marked for each of those measurements (length, crotch, back, and front, I used the average for each size), folded my fabric in half, and just cut a diaper shape using the measurement marks as my guide. Over time I've modified my pattern based on how it fits my baby, and even re-made a pattern based on his specific measurements, so it's a custom fit for him.
HTH!