lean weight gain
HRD-
Take the nutritional approach first before you try pro hormones and such. As an alternative to increasing your food intake, I'd try 3 protein shakes per day...
Early or pre workout/ 40g Whey protein (preferably an isolate Whey...CFM or Ion exchange...READ THE LABELS!)
Post workout/ 40g Whey & 75g Dextrose/Maltodextrin
Before bed/ 40g Whey/Casein/Egg combo, w Flax or Hemp oil (or powder)
If you want to add a non nutritional supp, try a micronized creatine @ 40 grams daily (4 10g servings mixed with 6-8oz grape juice) for 7 days, then 10g daily afterwards. Dextrose is cheap, you could add it to the creatine/grape juice (use more grape juice). You could also add ribose to the mix...dextrose and ribose DO have a synergistic effect w/ Creatine.
I've seen many first time creatine users gain 5-15 lbs in a few weeks w/ improved hardness and fullness.
But always make extra clean calories/protein your first priority.