Before you launch into the whole pattern start by teaching your horse to turn a single barrel. Start at a walk then work to a trot and then a lope. When turine be sure your pocket (space between your horse and the barrel) is even all the way around the barrel. Keep your turns as even and round as possible (rather than coming in wide and cutting close on the backside) in order to keep your horses hind end engaged through the entire turn. When you come wide and cut close on the backside some horses will swing their hindquarters around and disengage them. The are then not able to push off as fast to the next barrel. Also make sure to teach your horse to rate (slow down and collect) in the turns. When you get to the actual patter START SLOW! Make sure your horse is 100% at slower gaits before you add any speed. Trust me, it's easier to take time in the beginning rather than trying to fix it later. My favorite trainer to reference is Charmayne James if you need for info
Slow work, slow work, slow work! If you ask for speed to soon all your training is going to fall apart, be patient and do tons of slow work:) if may not be the most fun thing to do, but it pays off and it's the correct way💟 Have fun training your horse!!
Keep trail riding, helps keep them sane! Watch Dina Kirkpatrick on YouTube, she makes everything easy to understand.
Keep doing trails so he doesn't get fed up. But get your three barrels decide if you want to go left or right and start him with the never ending barrel pattern. So instead of coming home you go and make a loop and start over,make sure you teach him to make a pocket around the first so it helps him set up for his turns. Find a cue that will get him learning to slow down before every turn once you have him checked at each barrel and he gets that move on to a trot every once in awhile until he gets that down the the occasional canter but make sure he still checks himself before his turns. And then you go faster from there. That's what I do with all of mine and it works great
Do what melody said, but first work on his endurance and athleticism. If he only does trails, then before you go galloping around barrels, you need to build up his strength and athleticism with circles things like that spiral in and out.
I would buy 3 barrels to start (if you don't want to buy them you could use anything really , just make sure it's tall enough , I had a horse leap right over my "barrel" !) Them start walking the pattern, then trot, then canter. Watch lots of videos to inform yourself . Set up different patterns so your horse doesn't get bored. Hope this helps!