If you are just getting into this hobby, you might think that the biggest motor you can fly is a G-80. Fortunately, there is a much higher performance side to this hobby where you need certifications to fly certain motors. This is called high-power rocketry. To fly high-power rockets, you need to get certifications. Level 1 is for H and I motors, Level 2 is for J, K, and L motors, and finally, Level 3 is for M, N, and O motors. If you want to fly rockets at your first launch, it might be a good idea to attempt a level one certification while you are there. For a level one certification, you must be a member of one of two organizations, the National Association of Rocketry (NAR)or Tripoli. To get your level one certification, you must fly a rocket you built on an H or I motor and recover it in a state where the rocket could be flown again, also known as a reflyable condition. My recommendation is to buy a rocket kit from Loc Precision, like the Minnie Mag ( https://locprecision.com/collections/rocket-kits/products/minie-mag ) or a kit from Wildman Rocketry(https://wildmanrocketry.com/collections/wildman-classic ). The kits from Wildman come with everything except a motor retainer and building supplies like glue and epoxy. When you build a rocket meant for a certification flight, you should try to make it as beefy as possible in the fin fillets and any weak spots, as the leading cause for failed certification flights is a cracked fin. I would recommend trying to get the motor at the launch for a level one, so you don't have to go through the trouble of the shipping costs and the paperwork to get it online. Also, for motors, don't get a reloadable motor. Try to get a DMS motor, so you don't have to buy a reloadable case. After you buy the motor, you will have to build it. You and the person sponsoring your flight (watching your flight and signing the papers) will have to build your motor under your sponsor's supervision. Hopefully, before this, you simulated your rocket in OpenRocket, so you know how long to drill the delay grain. This delay grain is what the motor will be burning after the thrust of the motor runs out, so drilling it to the correct length is very important. Then put the motor in the rocket and let it fly. After this, you will bring the rocket to your sponsor to inspect. Then, after they sign the papers, you must send them to Nar or Tripoli, whichever one you are a member of; then, you are level one certified, so you can buy and fly H and I motors. But of course, for your first high-power launch, you could just watch as well, just bring shade, water, and food, and you should be good.
Links to NAR and Tripoli's site https://www.nar.org/ https://www.tripoli.org/