I wouldn't consider $3.75 cheap for arginine simply because an effective dose is between 4-8
grams and that would probably drain that bottle in less than a week. Seriously, no supplements are really that necessary...I mean think about it. For $50...hell--nothing at all--you can make gains of up to 2" (according to DLD) in a year from natural penis enlargment. Say $150 of arginine over the course of a year helps you gain an additional 0.25" (because it won't make
that huge of a difference, trust me)--is that really worth it? I only say this to save you money, but it is completely up to you and either choice is repectable.
As for gaining
weight, try the method I used to pack on 15 pounds of solid muscle (I promise that). I took 20-30 grams of creatine for three days straight and the next four days I took none. Repeat this every week until you stop making gains. Also, take 10 grams of l-glutamine after each workout, along with 50 grams of VP2 whey protein by AST, and 75 grams of pure dextrose [supplementdirect.com] and 75 grams of "complex carbs" (maltodextrin) [supplementdirect.com]. Add 5 grams of ribose [supplementdirect.com] to this slurry as well. I also recommend sodium phosphate by FSI (dirt cheap) which you can order from bodybuilding.com (and the protein from there too). It won't be as expensive as you'd think.
As for working out, I would do a leg workout once a week, and hit your biceps, triceps, abs, and shoulders three times a week...trust me on this one. Alternate bench press and one-arm rows during these three workouts as well.
This should help you put on quite a bit of size before summer ends. If you have any questions, I'd be happy to answer them.
-Gold