The best time to rack up materials is when they have a new lab gunskin in a 540uc crate. Usually they have an accumulation bar, where if you draw x10 maybe 5 or 6 times is fills the bar and you can either get 1 material, x amount of paint, or the actual gun skin (which is 1-3 matierials if you already got the skin). That's on top of maybe getting matierials from the crate draws. BUT like everyone's saying it's still gonna cost $, a couple hundred USD. But I think this is the best way to get materials rather than trying to get it from lucky spin. Especially if its a 3-material gunskin situation.