Many people wonder if they can use their child's regular clothing when they start cloth diapering. On the whole, yes. Some people find it necessary to make a few adjustments, though.
Onesies-Sometimes people starting to cloth diaper get a lot of leaks and don't realize that the onesies they use could be the problem. I still use onesies with my cloth diapers. Sometimes, though, if the onesie shifts in the crotch area too much, the onesie can wick moisture away from the diaper and cause small leaks. I find this happens most often with pocket diaper and AIO diapers. This happens to us less when we use covers or even one-size diapers. Diapers that are wider in the crotch area are also less likely to do this.
Pants-This can be another area that you may find you need to make adjustments. In sleepers and knit pants, I have never really found the need to size up so that a diaper can fit over my daughters' clothing. Dresses and skirts also pose little problems. Pants that are made from less stretchy wovens, like jeans, corduroys and khakis, have less give to them. You may find that a bulkier diaper doesn't quite fit under these pants. I have had no problem with pants like this as long as I use a trim diaper (see this previous post).
With a few adjustments, you should be able to use most of your current clothing. I've gotten to know which pants go best with which diapers or when I should use a fitted and cover rather than a trim pocket diaper. There are few garments my children really can't wear due to cloth diapers.