Brick.ie The Irish Association for Adult Fans of LEGO®

I'm kinda getting back into the Lego thing and looking at loads of inspirational stuff on the FB groups. While i have a certain amount of Lego built up as finished models I'd like to amass a stock of Technic and normal Lego pieces to start building MOC vehicles.

My question is: where do you seasoned pros get your stock from?

I've been scouting the local charity shops and there is literally nothing to be found. Anyone on donedeal seems to think second hand sets are worth nearly as much as new sets. At the prices being asked for some sets that are still available in the shops I think I'd be better off paying the slightly more for a brand new set.

So any hints or tips for an amateur trying to build up his stock?