as someone said before alot of great advice in here. do your research. alot of pros recommend to do dual joint movements for size, like barbell excersizes, not dumbbells. In most cases not all, dumbbells are used for shaping and toning excersizes, however amazing for isolating muscle groups. I would suggest to try only barbell excersizes for a short time and monitor your strength over a period of time and adjust accordingly. Remember your goals will drastically dictate what type of shape and size you would like to achieve. good luck.