Taking andro at the age of 16 is pointless. Natural test levels are nearing natural peaks and with proper diet, gains should come easy.
Even if you are in your 30's or older, prohormones are a waste of money. The conversion is weak, side effects common, cost ridiculous, and benefit far from gaurenteed.
Without knowing you stats or goals, I'll give a few quick thoughts.
If you want to grow, you must do a few things correctly.
1. Eat a proper diet - This is the MOST important aspect of making any progress. Everyone has different nutritional needs, but in general, be sure to get sufficient protein (1.5-2g per pound of LBM is a good start in my opinion) and keep dietary fats under 25%. Stay away from simple carbs. Drink LOTS (at LEAST a gallon a day) of water. Replenish evey lb of weight lost during a workout with 16 oz. of water. Eat a good meal within 30 min of a workout to promote a pos nitrogen balance (prevent muscle catabolism) and replenish glycogen stores. Eat healthy meals every 3-4 hours to keep you metabolism going.
2. Train properly - maintain good form, and stick stay away from isolation excersises until you are more experieced. Compound movements will build better, and will help you build tendons, ligaments, joints, and support muscles. Don't do any more than 12-16 sets per bodypart (3 excersises, with 3 sets each is plenty sufficient for growth if you use strict, proper form, and work each set till muscle failure).
3. REST- This is often overlooked. You don't grow when you lift, you grow during recovery. Be sure to get 8 hours of sleep a night, and allow proper recovery between working a musclegroup.
If you have those bases covered, add some multi-vitamins, Vit C, creatine, and Omega 3, and 6 fatty acids, and you should be gaining like a madman. Remember, to gain weight you need to take in more colories than you burn, so take that into consideration when planning meals.
Stay away from any horomone based supplements or drugs until you are at least 20. The male body doesn't stop growing until the age of 24. You can stunt growth by messin with horomones too early.
-FC