From all the research I’ve read the recommendation is to take calories for longer runs around 30min-45min.
When I go on longer runs of more than 1 1/2 hr and longer, I’ll take gels with me. These little packets are awesome way to get calories and sugars into the system. Over the many years of running, I have tried several different brands. Some are awesome and some are awful (Looking at you GU Hoppy Trails). That was a rough run. Here are some of the brands of gels I enjoy and use.
Huma

These are my overall favorite running gels. The consistency is thinner than some of the brands. The flavor of the gels are too sweet compared to others. The company promotes ALL NATURAL on their website. I’ve had 0 stomach issues with any of the gels.
Spring Energy

I’ve enjoyed using Spring Energy on my longer runs. The beauty of these little packs is that they have more calories than other gel company. Their slogan is Nature is Power. Awesome Sauce is a fantastic gel that taste like apple sauce! A Hydration drink mix was recently released and I have yet to try this.
Honey Stinger

Honey Stinger are typically known for their Stroopwafels but they make a great gel also. The consistency is thinner than the others and they are made with honey. This adds a more complex flavor in a good way to the gets.
Clif

I’ve tried quite a few different Clif gels and I absolutely love the Double Expresso flavor. This little pouch packs a punch with the caffeine and the coffee flavor is strong as well.
GU

The last gels on my list and one of the biggest name in the space is GU energy. There are so many different flavors to choose from. The biggest drawback for me is the thickness of the gel. These are much thicker consistency and requires a little more effort during longer runs to handle. If you have texture issues, I would look at other gels one this list