Here is my LEGO collection as of July 24, 2012. According to peeron.com I have a little over 18000 pieces, 154 sets, and 178 minifigures. I know all of my pieces are not sorted in anyway at all but I plan to sort them as soon as we move into our new house in about a year or so because I will have a bigger room. Right now my room just doesn't have enough space for all of my LEGO pieces to be sorted into separate containers.
Here are all of my minifigs!
I have all my minifig accessories in this box. They're a lot easier to find that way. These are the only pieces that I sort out from the rest of my LEGO pieces.
Nice collection. I bet you wouldn't have to build in rainbow color if you had everything sorted! :) But try to cover up the studs in your MOCs with flat tiles(this gives everything a smooth look, and also try to keep it this in one color too). And check out other people's MOCs and try out some different techniques of your own! Oh, and you can buy bricks you need for MOCs online. Bricklink.com would be a good place. I hope you take my advice!