If your looking to actually put on bulk I suggest eating a post-workout meal 1 hour before going to the gym which should be packed with protein.
Also don't eat straight after your workout, you need to stretch down then half an hour after your workout you should eat.
Also when your lifting weights. if 2.5 is the heaviest you can lift, do 10 reps. If you find it easy then the weight isn't heavy enough so go just a bit heaver and do 8 reps. do 3 sets off 8 on one arm and then again on the other. Once both your arms both cant lift anymore, then I suggest at then end of your session you do 10 minutes cardio. This wont happen over night but if you eat the right stuff like the saying goes: You are what you eat. Then id say maybe 2/3 weeks you should be able to see some significant difference.
Your session should be the maximum of just one hour. And don't do the same thing everyday, mix it up by keeping your body guessing. Like one day you focus on arms the next on legs, then back then shoulders etc...
If you want more information I suggest going to
http://www.menshealth.co.uk/
It will give you a wide range of everything and anything. From nutrition to muscle building. Just remember you have to push yourself, no pain = no gain.
I go to the gym myself so I saw this thread and thought "oooo I know this!" lol
Anyway I hope this helps :D