For your first bearded dragon, I would recommend buying an adult (at least 2 years old). Adopt one from a local reptile rescue, animal shelter, or off your local classifieds if you can — this is where you are most likely to find an adult beardie looking for a new home. They may not be as small and "cute" as the babies, but adults are more durable and more likely to tolerate common beginner mistakes.
Bearded dragons make great first-time reptiles — but be warned, their care requires a substantial initial investment. Because you have to mimic their native habitat in your own home, a lot of special equipment is needed. But don't let that scare you away. If you want a beardie companion, with a little determination you can make it work.
I recommend this care guide to all new and prospective bearded dragon keepers:
https://www.reptifiles.com/bearded-dragon-care-packet/
Bearded Dragon Obsession is a great group on Facebook to join for more information.
Be sure to also read the files here on BeardedDragon.org. There's lots of great info here!