How have people built up such large collections of bricks?
I would like to get into building Lego Great Ball Contraption modules, but this needs a lot of parts to play with. I've got some Lego from (30ish) years ago, but not much seems to have survived, and I've bought a couple of bug Technics sets - but I need a lot more Technics, plus more standard bricks, plates, smooth plates etc.
Buying sets is one way, but expensive and I don't like to just make them and then instantly dismantle again.
Buying on a site like Bricklink is great for specific pieces, or when I have something to get it all in the same colour etc.
I've seen random "1Kg lego parts" on ebay which I can try to use that to build up a load - has anyone tried this?
Or is there another way I'm missing?