Approaching the build with creativity and the willingness to experiment will yield the best result. Don't be afraid to mix and match blocks to accomplish a unique layout that works best for you.
Full blocks, half blocks and decorative blocks
Overlapping full blocks will provide stability and structure, but you may need to use a half block or solid block as a spacer or as a design element to provide variation from the others. In addition to standard cinder blocks, decorative architectural blocks are another option consider.
Cost
Basic cinder blocks are readily available at your local home improvement store. A full cinder block is very affordable and can be purchased for a $1-$2. Decorative blocks will vary in price, but be prepared to pay more than you would for a standard block.