Here is what one of my books says about feeding LAYERS. (different for meat birds)
Starter feed: 0 - 6 weeks
Grower feed 6 - 17 weeks
Pre-layer feed 17 - 19 weeks
Laying feed 19+ weeks
It says that if you are on a tight budget, you can skip the pre-layer feed and just start feeding them a calciun supplement of Ground Oyster. Your chickens also need grit to help grind up food to help with digestion. If you chickens already have access to grass/dirt or free range they are already getting grit. If they are on concrete or not able to get to dirt, you can get a bag of grit at the feed store. You can also give your chicken table scraps. Just don't give them raw eggs, onions, garlic or raw potatoe peelings. Chickens enjoy fruit, vegetables and greens. Mine love yogurt, raisins, grapes, watermelon, tomatoes, oatmeal, melon and old dog food. Just remember that if you are trying to grow "organic" eggs, feeding them non-organic food scrapes negates that.