You definitely want to try it more than once. Many babies won't like it the first time, or even the first few times. I've read that it can take up to 10 tries before they realize they like something. I wouldn't worry at all about him being a picky eater yet. Purees are really different from our foods, as it's a blah sort of taste. (I've tried em...they're horrible. Especially the meat.) Just make sure each time you wait 3-5 days in between to make sure he's not allergic to anything. I've also read it can take multiple times before a reaction occurs. Good luck, and don't give up or get discouraged.
YES, you definately want to keep introducing the same foods every few days. It may be they just need to get used to the texture or taste. If he gagged it's most likely the texture or consistancy that he wasn't used to. Just keep trying, eventually he will probably eat it. If after several weeks or trying every few days he still refuses then Wait a few weeks and keep trying. Baby's taste buds are still developing and their tastes can and do change frequently. Lily wouldn't eat the meats at first, but now she will...especially if they are cold. That's something else, try different temperatures. Some babies prefer certain foods warmer or colder. Like I said, Lily will eat her meats faster with them cold than room temp or warm.
Lily is pretty picky too but now likes some of the foods that she didnt a month ago. we do fruits with cereal and yogurt for breakfast , fruit/veggie blend for lunch, and a meat and veggie blend for dinner. we would still have to mix fruit with veggies to get her to eat them because she doesnt really like them (like her mom!) i have 3 flavors to recommend to get your baby to eat veggies for picky eaters. one is by "sprout" its carrot, apple mango - second is "happybaby" spinach, mango and pear, and third is "happybaby" broccoli, peas and pear. she loves all three of these, i get them in bulk on amazon.
I've been feeding Kaelynn puree's for about 3 months now. She still doesn't like the green beans or peas. I still give them to her and she eats them better not than before. I try them about once a week. I have noticed that if there to runny she wont eat them. I thicken them up with rice cereal. She loves sweet potato corn casserole her favorite. She's not to big on bananas but loves all the other fruits even mango one of her favorite fresh fruits I cut up for her. Maybe because I ate so much mango when pregnant.
I tried meat once and she refused it. I haven't tried it again. She gets quite a bit of table food were transitioning her off of purees. She's got 7 teeth now.