What would the "Pros'' recommend ?

I am working out but i am only 15 and i dont know if i should work out with low weight and more reps or high weight and less reps.....or something in the middle

Something in the middle. However it depends on what you consider high weight, low weight and more reps or less reps. Most of the pro bodybuilders do between 10 and 12 reps, 5 or more sets for getting definition and for bulking up they would do less reps,like 8 to 10. but for each set you should try to work up close to the maximum number of reps you can do. e.g. if you can do 15 reps with a weight you should add more weight and get it down to around 10 or12 reps. Remember this tho, every ones body reacts differently to the number of reps and sets so you'll have to do a little experimenting.