Finder Compass by atomicstryker is an invaluable tool for quickly locating ores. You can choose which blocks to look for–I chose diamonds, gold, emeralds, lapis and redstone. The recipe only requires 4 iron ingots and one redstone.
In the image (left), the compass shows the directions for gold, diamonds, lapis and redstone. The range is configurable but I left it at the default values.