Never ever ever ever mine straight down or straight up lava will hurt when it burns you mine in a staircase pattern then when you get to bedrock mine in a line. First look for iron ore it is the most valuable material to you right now. After you have smelted the iron in a furnace make a pickaxe it is the best tool to make first so you can mine diamond. Iron is everywhere you just have to look. Diamonds will be about 10-15 blocks above bedrock. If you are looking for Redstone or gold they are around the same place as diamonds.
