I was starving tho. My belly hurt
I always try to go on a empty stomach... Maybe a protein shake or the calories of an energy drink
But you trying to gain so you should eat regular meals before you work out (lifting)
Honestly, if you trying to gain you need to eat about twice as much on workout days then you normally do. Small meals though..
Those boost shakes you mention would be good for most of those meals. You not gonna get fat or nothing because you're actually working out and not just sitting around doing nothing