I'm currently mining amethyst in my spare time to get 10m for miscellania. Then about another 20m for construction (i've got 10m banked atm)
After that, are there any other things I need to save my money for? How long would it take me to make 20m just from comabt? Sadly level 70s combat and 64 slayer so nothing big fast. So I feel like amethyst is my best money maker right now
