Congratulations on your endeavor--I hope you find not only success at the end, but enjoy the process.
While there is no Hobby Official FAQ, it's a common topic--and it essentially comes to this:
1) Q: Kit or Scratch? A: Good arguments exist for both, and both have been successful. Your level of expertise, experience, and budget will likely dictate this better than some guy you don't know on an internet forum --or least, it probably should (so says the guy you don't know in an internet forum).
2) Q: Will XXXXXX Kit be good for L1? A: Probably. But if it's designed and sold as a MPR kit, realize it may require modification (omission of thrust rings, swap out of shock cord mounts, etc) to achieve the goal. Kits sold as HPR will need fewer, if any, modifications.
3) Q: 29 or 38 or 54? A: You can always adapt down, not up. And having a larger hole than you have hardware for is a spectacular rationalization, used amongst many experienced rocketeers, to acquire the "right" hardware. "But honey, these adapters aren't really the way to go, and present an additional point for possible failure. It'd be safer to get the right thing, trust me..."
4) Q: Should I read rocketry book XXXXXXX? A: Probably.
5) Q: I bought a kit by a well-known and reputable manufacturer, so I don't need to sim it in Rocksim or OR, right? A: Wrong. Simulations can save certs, rockets, and money. Good simming practice can be key to a successful flight. Perhaps you built heavier than the stock kit--is your landing speed going to be good? Is that motor going to bring you through transonic, and are your fins up to it? Is your CG/CP good, or do you need nose weight? How much wood could a woodchuck chuck if a woodchuck could chuck wood?
6) Q: Should I get the H-blah blahty blah or the H-doo-bee-dee-doo? How about the I-fah-fahty-fah? A: Your rocket, flying field, style of flying, budget, comfort level, experience and expertise --along with the sim-- will be able to answer this for you. It's YOUR cert. Do it how you want. I flew many H's and I's before I few an F (or G, come to think of it), and a K before I flew a J. Maybe you prefer a more linear approach... nothing wrong with that. Maybe you just want the biggest motor you can cram in there... have at it! If it's built well, flies safely, doesn't break, and recovers... cert is yours.
7) Q: What camera should I use to video the flight? I have a Idroid, and it's got a flexpixel with auto adjust and enhanced zoom focus something something f-stop... A: Someone else's--let them video. You watch.
Later!
--Coop