I've been in a discussion with one of our forum members about what to do to get started and rather than continuing with him in private I thought I'd just put my thoughts together in a post for everyone to read, comment on, and hopefully benefit from.
There are a lot of choices and it's easy to get caught up in analysis-paralysis where you get so bogged down trying to make the best decision that you can't make any decision. To get right to the meat of the matter, I personally think it's best for anyone getting started to just buy a basic quad and get it flying.
With a basic quad in your possession you can get to work flying and improving your skills while you get a handle on what you want to do next.
If you've got some experience with radio control planes/heli's/cars and you like to build things you can make your basic quad a little more of a challenge by building it from components. This opens up your choices as now you can consider any of the flight controllers out there (DJI, Mikrokopter, OpenPilot, Hoverfly, KK, Arduino, MultiWii, etc.) as well as motors and ESC's. Keep in mind though that this is supposed to be the quad you learn with and that will probably include some crashing, mistakes in building, and it may even fly away at some point so I highly recommend that you keep it simple and inexpensive. There is a lot to learn and in getting this first quad flying a lot of the mystery that seems to surround these things will just go away and you'll be ready for the next build.
If you go with a second build and decide to make it more, more, more of everything there's a chance you won't want to fly it for fun or in a way that will put it at risk of crashing. That's where the first basic quad comes in. If you've got a maneuver you're aching to try but it's risky, get the basic quad out. If you haven't been flying much and you want to get proficient again, get the basic quad out. If you just want to velcro a GoPro to the frame and take video of you flying after winter geese that are pooping on your lawn, get the basic quad out. I can't really enjoy flying my bigger heli because it's part of my business and it would be too expensive and time consuming to replace. With a smaller, more basic quad available I can fly after dinner and enjoy the hobby while keeping my working heli safe for paying gigs.
Hope that helps.
Bart