best depth to find gold ore terraria

Answer 1

Between 500 and 600 feet below.

Answer 2

There isn't a best depth however, after you reach 200 feet above ground and below you will find gold ore.

Also gold ore is usually 30 blocks or higher away from the previous ore.

However, do not go to hell as this will have only ash blocks, hellstone, hellstone bricks and lava.