Would like to make a flower garden and have no idea how

I would love to make a flower garden in my front yard. I was thinking of a round one, maybe 6' in diameter. It will all have to be a raised bed since I do not have the ability to get down and dig up the old dirt and roots. So I was going to put down some of that cloth stuff that you put down to keep the roots from coming through. Then I will put the dirt on top and at that point I have no idea what to do. I've never made a flower garden in my life. I have hundreds of plants indoors but I want something pretty and colorful outside. So I'm all eyes and ears. How deep do I have to make my soil? I was thinking of using some stones or bricks as an edging. This is all I know to do. The rest is up to you guys to tell me. I'm a total newbie to the outside world of gardening but I'm good at following directions. So please don't hold back, I need all the help I can get. Oh, I don't have anything esle in my yard so this will be the main focal point to start with I guess.

Thanks,
Jesse