Hi,

I've been collecting technic sets for a few years, mainly buying the larger ones every year, for the looks and complexity. But I've lately been interested in building GBC machines and wanted to know how to get started building a collection of bricks for this purpose. Is it better to buy stuff for this purpuse from Bricklink or are there any sets that/themes that are better suited?

If, as you say, you have several of the larger Technic sets at home, the only thing you need to start building your own GBC modules is a couple of balls (or beads of the same size).

LEGO Sports balls cost a fir bit on bricklink right now so I would go with some 14mm beads off eBay to get going they are the same size and weight so will behave in the same way as the real thing. Build something small and go form there