i play college football right now as an offensive lineman so i know all about gaining weight =D
First off, don't worry about taking supplements to help your growth. In fact, i highly encourage that you use some type of protein supplement. Whey protein is what i've found to be the best. I live in the Texas Panhandle so i get plenty of protein via steaks ;-) But do indeed take supplements, they help so much. Creatine is great too, but i understand what you mean by it all.
Curls are for girls. If you want to fill out the sleeves of your shirt, then work on your triceps. Don't neglect your biceps though, cause every muscle is a good muscle. Your bench press max will go way up when you start building some monster tri's. Have you ever gotten the bar to where your elbows make a 90 degree angle and then dropped the bar on a bench max? That's when your tri's come into play. If you ever take up powerlifting then you'll use bench shirts which help you alot untill you get to your tri's.
Leg strength.. hmm.. squats are the probly the most effective way to get to your thighs. There's not a football routine in the country that doesn't use squats. Try doing some front squats. That's when the bar is resting on your chest rather than your shoulders. If you want to develop some acceleration and crazy speed for scrambling, develop those calfs too. Calf raises are good but they are boring so there's other stuff you can do. Get on a stair master and don't let the balls of your feet ever touch the groud. Or just walk a lap on your tippy toes, it will burn
As for the chest, someone already kinda hit the nail on the head. Bench press, flies, push ups, etc. If you'd like i can send you a college work out so you can get an idea of what to do.
To build mass: Heavy weight w/ low reps.
To build stamina and develop cut muscles: low weight w/ high reps.
Don't forget the incline and decline presses either, they'll give you a huge chest too.
Remember that every pound you put on, the longer it will take you to run that almighty 40 yard dash. Run every day you can. Running up a hill or running bleachers is a really great workout that will take less time than running 10 100s.
And last thing.. Yes free weights are the best. They make you concentrate on your work out alot more because of balance and that used more muscle fibers. Have you ever done lat pulls and felt nothing? I don't know why, but the back muscle will not develop unless you concentrate on it. During your rep, vision what your back looks like and what your muscles are doing while you pull the weight. Concentrate on every work out and you'll feel a difference. When you use free weights, you're way less likely to just do the weight and rack rather than concentrating.
If i remember anything else, i'll post again
**Sorry this post was so long.. I know way more about working out than i do reptiles so i needed to speak about what i know when i had the chance**