Now, a little about me before I put in the weekly plan I've been working on. I'm 28yrs, 5'10''-11'' (181cm), and I weigh only 154lbs (70kg).
Before I discovered this site I purchased one Dumbbell of 20 pounds, and started doing exercises I knew for Biceps, Triceps and Shoulders. I didn't even take daily breaks for muscle groups, that is - until I found this site and started reading everything what was explained here. In meantime, I did gain some muscle mass on the mentioned muscle groups, and I think I even gained a pound or two of weight (I think I was like 152lb when I started).
So, this initial "success" got me thinking that I should go for other muscles of body. I decided (and realized) chest needed widening, butt to be bigger, and also leg muscles. I also included some practice for ABs as even being this skinny started to go round too much. So in general I decided that I wanted to get larger

Here's a plan I made, in which you will notice I respected some of the rules I learned here (for example: 48hours of break between muscle groups):

The dotted parts are the alternate exercizes.
So any tips corrections I should do here? For example I'm wondering whether I should do all of the biceps, triceps, shoulders in one day?