Airline will not upgrade just like that because there are seats unsold available in upper class the one you sit in. May be earlier it use to but these day it is not that easy. If an airline offer upgrade to some passengers then you should know points of charging premium price for such class.
There should be a push or pull factor in this upgrade. This push factor can be when flight gets overbooked for certain class and above empty seats. They are forced to decide give offers upgrade airline tickets of favored passengers few. Loyalty is a big ticket got from travel hacking.
Pull is about strategies that passenger should employ for getting themselves in the world. Since the points you have balance is not enough to fly on same airline or other airlines of same alliance, it cannot be practical. So it is worthwhile to sign up for credit cards of airlines that come with lot of points. But beware of their annual fees and some minimum charges.
Flight upgrade with travel hacking
Upgrades generally functions from loyalty or money spend. If you fly frequently especially business trips you can stick with one airlines and frequent flying program of that airlines will become an elite. Loyalty programs are created specifically and it works also. So you can find those companies with which you can fly many time. Sometime it may not possible if fare is more or available seats is less but try booking by changing dates or destination. Such a way you add up your points that get add to free flight and hotel discounts. Again it has to be fast to earn points for free travel. You have to kick things really to your notch to get into travel rewards and upgrades.