check out some of the earlier posts in this thread for info on covers and folds. Nelle (moderator) has posted some great info, and if you click her name you'll find links to instructograms!
night nappies, here we use a specialised MCN night nappy with a pair of woolen longies or a fleece cover. DS can out-wee 18 layers of super-absorbent bamboo, so a terry flat just isn't going to do the trick!! If your bub isn't a heavy wetter, you could try folding a microfibre, hamp or bamboo booster into the nappy for night time. Microfibre cloths can sometimes be found in the auto section of discount stores, Kmart etc, and it's quite possible that will work just as well as an expensive store-bought booster. Hemp or bamboo is more absorbent and naturally antibacterial, though. Most online MCN stores sell various boosters separately.
The plastic pants and pilchers you get from Kmart, Big W, whatever, are just that - plastic! Not good for bub's bot. They don't "breathe". PVC is actually banned in children's products in some countries. Look for PUL covers, and good quality fleece like Malden Mills Windpro. And for woollens, check out Possum Pouches for hand-knitted soakers and shorties. They also have affordable night nappies and MCN that are AIOs. Fleece can be machine washed between uses (if using overnight) or aired and rotated between a few covers for daytime. Wool needs to be lanolised and handwashed maybe once a month, and just aired in between wears, unless it gets soiled. If you knit, or have a rellie that does, maybe ask them to make a soaker or a pair of longies. Patterns shouldn't be too hard to come by online. Just make sure it's 100% wool, and lanolise before using. HTH!