What branch of the Military do you suggest for me?

I am 18 about to turn 19, currently headed down the wrong path. I feel the military is the best way for me to straighten myself out and gain discipline and respect. I can't lie i don't have much knowledge of the Military branches. I am looking to hear from people with experience or knowledge before i speak to a recruiter trying to meet his quota. The only one's i'm really considering are the Navy, Marines, and maybe Army, maybe National Guard. Im starting to think differently on national guard the more i hear about it the more it sounds like a job than a disciplined military branch. No disrespect intended. I am looking to study while enlisted. I wan't a steady income, maybe a nice sign on bonus to put a downpayment on a car when i return from basic training. Please help me out as i am looking to enlish as soon as possible. Oh and the only reason i'm double thinking the marines is because i honestly don't know if i would be physically able to endure the training, im very skinny but im trying to get my weight up. i know i qualify but just by about 2 or 3 pounds, im 5'8 and about 125-130 lbs.