Gagging is nothing to worry about - it's how he learns how to move the food around in his mouth. They get passed it pretty quickly if they get practice at the lumpy foods. If he vomits I would clean up and carry on with the meal, don't get upset. If it keeps happening after a few days of consistently offering lumpier foods, then I'd take him along to the GP as he may want to be seen by an SLP.
At this age he can really eat anything that you are eating! Pizza, roast chicken, mashed spuds or baked/roast/boiled... pasta, cauliflower cheese, shepherds pie, fish pie, noodles, soup, mild curry - the only things I would avoid is obviously anything with lots of salt and/or sugar added (in other words, most ready made meals) and nuts (if there's a history of allergies)