Get 99 prayer, herblore, smithing, construction and summoning :P And if you are those skills already 99, then chin 99 range, barrage 99 magic, etc :P Or have a drop party :) Investing in the market could be good too, surely because there's for many items almost 50% inflation over 180 days so that means you would have 60m if you invested that 180 days ago :P