Actually, if you have gold left after the event it'll turn back into ingots again.
So if you start a game with 24k gold, buy an item of 4k you'll still have 20k in the next game.

I have 570 jade things now, two times 250 from the event and the rest from around 15 games or so.

Just buy movement speed items, go Veno and drop wards like crazy.
Also the mines and firework are really handy, too bad most people are fucking greedy and wont buy them.