should deca be my first cycle?

[TheCoop]

I am 20 and 140 pounds of lean muscle i eat right and work out hard, but i can't gain weight. So one of my friends said i should try deca. Should Deca be my first cyle and if so should i take something else with it to keep the gains. Also which is the steriod with least amount of side effects. I really want to do this, but i want to make sure i do it 100% right the first time.