Always do milk first. It's much more important for nutrition- at this point food is just to practice eating. At 5 months lots of babies haven't even started on solids, so no need to push it. Add about 1 new food every few days and mix it up. Good early foods include avacado, sweet potato, banana, peas... "Super Baby Foods" by Ruth Yabon has a great list of foods to introduce at each age, along with good suggestions on "recipes" (although really once my son had eaten all the ingredients to a particular "real" dish of food, we'd just take some of whatever my husband and I were eating, run it through the food mill, thin out the consistency, and feed it to him).