If you've just started then you can make some good improvements in the next few months.
With your diet, make sure you're eating at least four meals a day. Try to keep them as clean as possible, not junk, and avoid too many snacks, as you don't want to be adding weight just for the sake of it. If you're working long shifts, you're gonna need to find time to get in a couple of small meals somewhere.
It's way too early for any supplements really, but a good multi-vitamin/mineral is always useful.
With training, keep to the basic movements for the time being. Concentrate on getting the form right before you start piling on the plates. If you get into bad habits now, you'll be lining yourself up for an injury later on. I'd probably be looking at something like this:-
WORKOUT A
Squats - 5 sets of 20/15/12/12/12
Bench press - 4 sets of 15/12/10/10
Bentover Row - 4 sets of 15/12/10/10
Shoulder Press - 3 sets of 12/10/10
Barbell Curl - 3 sets of 10
Dips - 3 sets of 10
WORKOUT B
Deadlifts - 5 sets of 20/15/12/12/12
Incline Bench - 4 sets of 15/12/10/10
Chins - 4 sets of 12
Dumbell Shoulder Press - 3 sets of 12/10/10
Dumbell Curl - 3 sets of 10
Lying Triceps Extensions - 3 sets of 10
Alternate the two workouts, leaving 48 hours between each one. Again, don't worry about the weights you're using, just concentrate on doing the movement correct. Smaller muscles like calves, abs, forearms, can be fitted in where you wish. With about 90 seconds rest, you should be in and out in an hour. Make sure to take in some simple carbs after your workout to replace glycogen stores, and some protein within an hour or so.
Anyways, that's my thoughts. The important thing is to look around, do some research and try different exercises to see which ones you like. Everyone has motivation when they start, but you need to make sure you enjoy what you are doing to keep that motivation going. Everyone can give you lots of different opinions on what to do, but you need to find out what works best for you.
