Going around begging is likely a bad idea.  I recommend The Deck Builder’s Toolkit, which comes with 285 semi-random cards for about $20 USD.  It comes with some booster packs so you have a chance at some rares as well.  It’s not the thing to start trades with though, since the rares are light.  Anyway, try starting there.  Also, be aware of the joys of networking with your friends and players at your local card store.  Many people will give up their commons and uncommons and rares they don’t need.