How do I get my 9-month to eat finger foods?

My son is 9 months and I feed him by spoon Stage 2 baby foods. Occasionally, I mash up bananas and sweet potatoes but also feed by spoon. He still does not pick up any food by himself, and the few times I tried to give him little squares of ripe pears or lumpy Stage 3 food, he swallows so aggressively and gags. It's so hard for me to watch. Everybody tells me to give him Gerber Puffs but I find them to be so hard; I am certain he'll gag. Any advice on what to do next (what kinds of foods) so we can move on to teaching him to feed himself? Thank you kindly.