Beatrix is the best gold-liner

In the early game, farm carefully, trying to avoid dying as much as possible. If you're being throttled, ask for active help or try to lane with exp. If you see that your enemy is more passive than you, you can dominate the lane. In the mid-game, you'll gain damage and can actively engage other lanes while still maintaining farm. Also, don't forget about pushing, as Beatrix has fairly good tower damage. You can win the game with just two weapons: a cannon and *******; the sniper rifle and shotgun require some practice. Also, the shotgun is only used after purchasing the green upgrade.