If you are a level 3 woodcutter and don't say much, you get more randoms. I've tried that and it works. Sure people say a random is a random but there are certain randoms that you can do something to better your chances.
Just mine the iron first, it's not hard. I bet if you worked hard enough, you can get 2.5k iron ores in one day. Then slowly mine the coal, you'll get it soon. Or think of it this way, if you don't do it now, you'll eventually mine that much iron and coal anyways.
Well I'm currently mining 2k iron and 4k coal. Iron: I'm mining at the West Varrock mine because it is usually less crowded, and I get about a load every 2-3 minutes (including walking to the bank and I'm level 66 mining). Coal: In the Mining Guild, I usually can get a load every 5-10 minutes (including walking), depends on how crowded it is. Hope this help and good luck!