I have a 'waiting period' for new family members that don't come from the toy store. They must have a character and that character must remain strong over the waiting period, and it's allowed to migrate from one wanted doll to another. I also have a certain look for most of my dolls that I want which makes it a bit harder to find them. My wallet thanks me.
For example, baby Alistair (in my icon ATM). I knew he had to be Yo-SD 1/6 size or smaller as he would have a bigger sister and he had to look like his parents. I could have bought a dozen sad looking tinies but I also put a price limit on him so he couldn't cost more than his parents. As luck would have it full set Brownies were on sale, then came the perfect Ha Ha face. It took a good 18 months to find his sister and wait for her to come in. Again, she had to look like her family.