Get close to the same size as in either standard chickens or bantam chickens. I have tried pure flocks of all of one breed but really have found, I like a mixed flock so that I can tell them apart. Getting different colored eggs is also fun.
Standard chickens that are good to start with, should be easily obtained are Black Astrolorp, Buff Orpington, Easter egger, Leghorn. Hoover offers a green and blue Easer egger. Some people worry that production birds lay too many eggs, and can later have reproductive issues, but I have been pretty lucky.
Being as you are new - do consider the space. Chicks are so tiny that what seems like more than enough space for chicks, rapidly becomes not enough space for adult birds. It is just a rule of thumb, but 4 birds should have a coop of 16 sq feet, and a run of 40 sq feet. Give or take, but pretty close. Overcrowded chickens can cause ugly behaviors.
Do know that being raised together has almost no influence on long term behavior.
Mrs K