Do a little bit of farming runs. Even if you only do one per day, and only one location, you'll earn cash consistently (that's my method RuneScape Gold, and I've got an 8mil account). You could possibly train to be stronger on lesser demons. they're now dropping ashes that cost 600 gp, along with some other items that you can elch. Guthan's strength would be a huge help but you'd be unable to afford it for a long time. Kill them at the Karamja spot close to the lave-thingies.

Every now and then Try to find the most evil tree to take down. They have a nice reward worth a bit to locate a yew tree that you can take down, while the auto-banking effect that is still in effect. Auto-banking is available for a certain amount of minutes depending on how you contributed to killing the tree.

It's not the fastest route to 10M, but it's steady and will bring you there eventually. The goal of this kind is hard to achieve because there is always a temptation there to spend it on crap but to do it using one of my methods:

Buy 10k of oak planks at -5 percent and then see if you get any. The 10k is merely test to see whether they will buy. You must wait 5-10 minutes. If they don't purchase, then increase your bid 1-2gp until they do buy. Sell 1-2gp under middle price.

Typically, you'll receive 10-12gp from each plank of oak (which means you should decide on a price of 13-17 below mid) It may seem like a lot RuneScape 3 Gold, but the next time you'll be getting more and and more...before your eyes blink, you are trading 25,000 per week and pulling in 300k per trade.