Advice please

My son has been eating baby food for about 4 months now. I keep trying to introduce baby food with thicker consistency and with small chunks of fruit and veggies and I have also tried those little puff cereal things too. But he gags when I give him anything other than completely pureed food. My biggest fear is him choking on something that he isn't ready for. Should I wait a little longer before trying again? Or just keep trying a little more each day?