If you were to get hold of your own old baby clothes, you'd probably notice they were a big roomier in the back than baby clothes are today. This is because back when you were a baby, cloth diapers were at least still used a lot if not the primary and preferred method of diapering. Around the time I was a baby, disposables were just begining to gather steam and my parents used cloth only with my older brother, but a mixture with me. Seems I suffered the same affliction as my little guy - yeast rashes.
These days, we have so many cloth options out there that the only problem is finding clothes that fit your little one. Chances are, t-shirts will be true to size, but pants are another issue. When Jack was a bitty thing, onesies were an issue. There are, as I see it, two main options.
First, buy a pack of onesie extenders. We have them. We hated them. But many, many moms swear by them for cloth and sposie bums alike as a great way to extend the life of your child's wardrobe. For us, we turned onesies into t-shirts after about 15 months and haven't looked back. For a pretty tiny price, you can give them a shot.
Second, buy the next size up. This is what we did for a long time, until somewhere around 15 months when we suddenly found that Jack's clothes fit better than they used to. If he weren't so tall for his age, he could still be in 18 months size.
As far as where to shop, I have found that the 5-packs of Carter's onesies are longer and stretchier. Knit is your baby's friend! They have some great little knit pants that come in two packs. I have also found that their onesies with snaps ont he shoulder are not as long or stretchy. If your little ones is on the shorter side, you may find that they fit well in Children's Place and Osh'Gosh. Thesir clothes all seem wider to me and shorter, so I imagine they are great for cloth bums on shorter babies.
We didn't even try to put jeans on Jack much before the last few months. Because he does seem to fit in his size better (he's 90th for height, 50th for weight), we are able to get by with one size up IF the jeans have those adjustable waists. I have to yank them all the way out to make the waist fit, then cuff up the bottoms.
Another option is Baby Legs! They are perfect for cloth bums, great for diaper changes and potty training, and look adorable.
Because of our current situation of being half moved and not at all settled, we are waiting until we ARE settled to get Jack potty trained. All the experts seem to agree that in the middle of something like a move, its best to put it off. So we have the groundwork laid and I have high hopes that this year's clothes will fit next year, too, once we get rid of that big bottom!