You would need a contrasting color. Typically half of the log cabin strips will be dark and half will be light. Although it would be possible to use only dark blues and light blues, since you already have a range of blues from dark to light it would make sense to choose another color for the contrast. It could be just one color, such as cream, or it could be multiple tones of cream. For the contrast, you probably would want to stay all light but it could be different fabrics that are all shades of light cream, for example.
Most likely the pattern is calling for 8 strips of blue and 8 strips of contrast.
Do not do foundation piecing if you plan to hand quilt. The foundation will make it much harder to push the needle through the layers. Experienced quilters would not even try this.
If you do foundation piecing you can still use a batting. There are many different types of batting, and some are quite thin.
There are different techniques for making a log cabin. Strip piecing is a very easy method and is the one I would suggest. With this method you do not cut the individual logs first. Basically you cut the centers, strip piece them on to an uncut strip of the next fabric (butting the squares right next to each other as you sew), cut them apart, press, then strip piece these partial blocks on to the next fabric strip. There must be websites with tutorials on this method.
I am experimenting now with cutting out all the logs first (something I don't normally do) and am finding it less satisfying than strip piecing. For one thing, it takes a lot of time cutting before I can sit down to sew (because this is a scrap log cabin); for another, I realized I already have made a mistake in cutting sizes (certain sizes should have been dark while others should have been light).