im the same age as you. got out when i was 24. did over 4 years n some change.
at YOUR age... if you decide to enlist, you need to figure out while you in if you wanna do 1 enlistment or go for 20. dont be that guy that gets suckered into 2 contracts n then decides he dont like it n gets out at 33-36 years old. if you dont wanna do 20 years do a one n done(3 year).
for army youll get promoted fastest in combat arms(i was 11B) but i dont recommend that. go for the chillest job possible that will give you time do use your Tuition Assistance while you in.....or pick an MOS that will give you valuable training and certs that will be useful when you ETS. best if you can find somethin that provides both. The more school you can knock out with your TA, the more of your G.I. Bill you'll be able to use. lets say you get an associates while you in. when you out, use that GI to finish your bachelors in 2 years, and then you got 2 years left on your GI Bill so theres your masters, free of charge.
this is a good time to stack. you single? dont eat at subway with your battle buddies. fukk that, eat at the DEFAC. dont spend 1200 bucks in one night at the strip club after deployment, dont get married dont get married dont get married, and dont buy that Charger/Jeep/Camaro you always wanted.
Let the army pay for your school, your certs/training, your meals, etc.
the only thing you should be spending money on as a single dude in the barracks is your phone bill, clothes, etc. you can really build a nice nest egg for when you get out if you play it right.