I am not a good scrappy quilter. I make a single block of any new pattern, making sure it works and comes out the right size before I cut all my fabric. If I were doing a scrappy, I would probably print a log cabin guide sheet, and then write in what is supposed to be in each block. I would sort as dark, dark medium - then light only or light, then light medium. Write in each section of the log cabin printed guide block which bag or box or pile to pull from, and start sewing.
This is an interesting webpage with some good Log Cabin info and several different pattern sheets in the lower porting of the page.
http://www.quilt.com/Blocks/LogCabin/LogCabin.html Use Yahoo or Google to look for ones you want to do.
Since you aren't very experienced, I would think about 2 1/2 inch strips for the logs. That way you can make a fairly large block pretty quickly. Results were and still are very important to me. Too many little pieces and I can get bored with a project pretty quickly. The 2 1/2 inch strips work in a lot of other strip projects so if you cut too many, not a problem, plenty of free patterns out there to use them in.
Quilting is such fun, very aspirating and beautiful, all at the same time. Welcome to our world.
Edited to add: I have seen log cabin blocks made with all brights or all darks, but the log cabin pattern doesn't show up very good. To me, it becomes too jumbled, but then I think the same thing with most scrappy projects I try to do. Quilting is all about what you like and want to do.