There are different ways to carry mags depending on what you are shooting.
For IDPA, I carry a double pouch on the belt with one mag in the pocket then I use that mag to load the pistol. I have a vest with extra mags in a few pockets. For the Steel & Paper Challenge, I wear a belt with a pair of quad magazine pouches. I place 4 mags in each pouch. If I shoot USPSA type events, I wear a belt with 4 or 6 pouches depending on the stage design and round count for that match.
There is a magazine you can get named "Front Sight". And at the end of a season they list all the popular products. You can research this and see what brands and models most of the shooters use. You can also at least attend your first match and just look at what they use and talk to the people that are shooting.