Normally, when I wake up I don't have any hunger. I eat directly at 12:30 sharp due to work hours so I can go to the gym in afternoon? My question is: how much time should I wait for before I work-out?
Just give it enough time such that you don't puke during your workout. Some people I know can go 25 minutes after their meal but others maybe hours. Of course you don't want to go IMMEDIATELY after a meal. This also depends on what type of workout you are doing (you might want to give it an hour or so if you are going to do stuff like crazy jumping).
In my opinion, the answer here is somewhat subjective in that the bodies of different people handle exercising on a non-empty stomach differently. The general rule I've found is that you don't need to wait after a light snack, you should wait an hour or two after a light meal, and you should wait three to four hours after a heavier one.
If you eat a typical lunch, you're probably looking at being able to work out within an hour, enough time to digest a decent amount of the food so as to avoid stomach cramps and nausea.
First and foremost, you are following an extremely unhealthy approach. You need to have breakfast or eat within an hour of waking up. This will kick-start your metabolism for the day. Google skipping breakfast to understand what I mean.
As far as your question is concerned, it really depends on what and how much you eat for lunch. Ideally you can hit the gym floor about 45-60 mins after meal.
-- Update -- Breakfast most important meal