You don't need a serger to do a "mock serge". This involves stitching the fabric as close to the edge as possible, then trim it closer after sewing if needed, then zig-zag the edges to keep them from unraveling in the wash.
Thick fabrics really don't work well with turning and topstitching. Do make a diaper with that technique, you need to have a thinner fabric for the outer layers, and thick absorbant padding sewn inside- but not all the way to the edge seams. It makes for a more complicated sewing pattern, but the end result can look quite professional if it's done carefully. The mock serged edge is just as practical as the "real serge" but doesn't always look quite as neat or professional. It also takes twice as long since you need to stitch twice. (Then again, if it takes you half an hour to rethread the serger every time the stitches get tangled, it can be quicker to do a mock serge- which is why I sold my serger a few months after purchasing it!
)
I sewed most of my son's diapers, but I couldn't compare them to prepackaged diapers because I never used them. The ones I sewed were certainly more absorbant than the cheapie prefolds I'd originally purchased as burp cloths- I could use one handmade diaper at a time where I'd need to double up on the cheap ones.
The first diapers I made were from an old king sized flannel sheet set, and I made DS a set of contoured diapers that fit in size large wraps. When he outgrew those, I made him side-snapping fitted diapers with interlock for the outside and several layers of french terry for the soaker. These diapers doubled as training pants since they could slide up and down easily.
. It's a lot of fun to make fluff for your own baby 
, Mama and educator to 3 girls and another on the way in July
