Minecraft help, mining ores?

ok, so im the luckiest person ever with mining straight down, i mine a 1x1 hole in the ground, mine the eight around that and keep doing that until bedrock, but all i ever find is iron, im not complaining, but i want a dungeon or diamonds, all i have for diamonds is a diamond sword, then i have iron armor and iron tools, but i want diamond tools, i find lots of lava pools, i use three buckets to slowly get rid of the pools and i find tons of obsidian, but i dont have a diamond pick to mine them and get a portal to the nether, and i want to make a temple around a portal, is there any fatser way? i also tried blowing away the top layers of dirt and cobblestone that have coal, but that sometimes hurts me