My lo gagged so easy, I couldn't believe it. I started with Cheerios for finger foods and she would gag and vomit, she got to where she would gag when I showed her a Cheerio, it was kind of funny, well if I hadn't been so worried that she would never be able to eat. I just started mashing things with a fork instead of pureeing them, then cutting into tiny bites, then small, then bigger. She is still picky about texture, if she doesn't like the texture of something she just opens her mouth and lets it fall out. But I keep giving her things even if she hasn't liked it before and somethings she has changed her mind about, like cooked carrots as long as they haven't been cooked to long. So don't give up, he'll get the hang of it, some of it also might be his age, maybe try when he is a month or two older.
