What sort of chickens should I purchase?

I would consider getting Barred Rocks. Their good egg layers. They are very docile and have great egg productions. They would go great with your Rhode Island Red chickens! Barred Rocks have black, grey and white spots in a pattern covering their whole body so their really easy to spot with your Rhode Island Reds. Barred Rocks would be the best in my opinion. Good Luck with your chickens! :)