You see guys, this is why you ask for ****ing stats before you give out advice.
The kid is 157lbs at 5'9 and only 18 years old.
Listen stop thinking your going to gain at least 20lbs or whatever ridiculous number you decide to put in your head. You need to understand what you are about to do is going to do more harm than good.
First of all the structure of dbol makes it highly suceptible to bloating and water gains, you realize why you will only keep less than half of those gains? Because most of it is water so when you get off the water will naturally leave as estrogen gets lowered.
Dbol only cycle produce minimal lasting gains, not tell me for 10lbs you are willing to sacrifice lowering your natural test levels, because even with PCT there is a good chance you could shock your HPTA and it might not fully recover test levels to what they were before.
Bro, trust me I have been there, I was a 6'0 134lb pound kid in high school, let that sink 134lbs, I was depressed and never thought I could gain weight or pack on muscle. One day I had enough of my sob story, so I signed up at a gym and just ate a **** ton of food, you cannot believe how much food I would eat everyday and trying to keep it as healthy as possible, I would eat till I wanted throw up.
4 months later I weighed in at 174lbs, everyone thought I took steroids and yet I never touched a supplement besides protein and rumors spread and I maintained my body and kept going at it and learned even more about lifting and dieting and kept advancing.
Not only are dbol only cycles not recommended, steroids in general are not recommend before 25 years of age (at least 21).
I mean do you honestly want to be 5'9 for the rest of your life? It's a great possibility because what makes growth plates close is high estrogen not the steroid itself, so taking a compound like Dbol that converts highly could very well put your growth plates at risk of closure.
Your choice, currently I am 6'1 and if I was in your position I wouldn't give up 4+ years of growth in exchange for 10lbs of muscle. You have all the time in the world to get bigger, you only have certain time frame to get taller and grow hormonally.