Hi Okye, welcome to BYC! What kind of chickens do you currently have? We have a mixed flock of 16 (Speckled Sussex, Rhode Island Red, Easter Egger, Black Australorp, Red Sex Link, and Barred Rock).
When we first got into chickens we purchased 7 from someone on Craigslist. We lost 4 of them within 2 weeks and ended up with only 3 (we call them our rescue chickens because they came from such a poor environment). Earlier this year we ordered from Murray McMurray and got wonderful, healthy chicks. Some people have good luck buying locally from Craigslist, but after our 1st experience, we decided it was worth the little extra cost (shipping and immunizations) to order online from a reputable hatchery.
No matter how you go about obtaining more chickens, make sure you get them from a reputable source and that they are the healthiest ones you can find. It's worth the extra diligence to be happy with your flock.