Play defense. I wasn't in your game so I can't possibly know what you did afterwards but every time I am in a game and one team gets first blood. The snowball doesn't come from the gold bonus (although it is a lot and makes it easy for them to control altars as well... thats just ****ty new map tactics) but you need to stay under turrets, or just outside of the range. Try not to let turret take all the CS but definitely don't go out to far. This new map is small and ganks are constant. Most people won't be able to call mia before someone runs top, especially if they are in a heavy fight themselves. So pings are an absolute necessity. But Defense is the main thing. Just wait it out. FB gold bonus is only a lot at first when everyone only has 1000g. But if you wait it out and don't give up and more easy kills by being over extended and keep getting CS and roam jungle after you push off turret. You should be able to come back. FB gold bonus is nothing once everyone has gotten around 2500. It will take awhile and you will have to play smart.
Another thing: Don't give up FB. The new strategy is some bull**** stand off on the sides of the speed boost and it's a terribad strategy. It's a toss up on who lives and who dies. I have seen tanks go down first in the first fight. Some team comps are almost unbeatable at start as well. So just play it smart. Stick together and stay out of that. Or sit on turret until minion spawn. That first fight is a gamble to hope you can get the snowball advantage. If you don't like loosing it and can't comeback. Don't give it up by not gambling on it.
The tutorial says it best. "Stay behind your minions"