first of all.. 72kg and 6' high.. and overweight? id say underweight.. im a bit more than 6' tall and im closing up on 80kg and im skinny :S
As for your consern weights wont make you bigger because you cant lift enough.. the muscle doesnt know how much you lift, it only notices how much of your max it lifts, so if you want to get stronger you should lift heavy (heavy for you)
lets imagine my 1rm for deadlifts is 200 and yours is 100 (just picking easy numbers here xD)
the 80% of my maximum is 160, so i must lift that or above to gain strenght (80% of 1rm or above gives you strenght)
yours would be 80kg, even though yours is smaller than mine, it will still make you strong.
Same goes for bulking only that you need other % of rm.
If you want both str AND size it can be hard. Though, there is a program called Bill Starr's 5x5 which i was on earlier and i had both size and strenght gains, you might want to check it out
Though if you just started, you might want to look around for a more beginner routine, i dont know of any, but someone else probobly does.
hope that answers some of your questiones and dont be afraid to be weak, i was very weak once too.. embarrased in the gym, but you get over that pretty fast, ive never once gotten a comment like "you really dont lift much" or anything like that
and if you choose to go with that program or not, learning those lifts can be hard, so be CAREFUL! if you cant do 5x5 with weights on the squat, do it with bodyweight
just remember that form (technique) is everything