I'm sitting on around 11-12M and I'm looking to make more. I don't spend much money at all because I tend to enjoy the gathering skills such as WC and Fishing, which takes up most of my playing time. I'm interested in learning how to flip, invest, and solo merchant. If anyone has any tips or would prefer to link something to me, please feel free. I'm eventually wanting to hit 100M+. Thanks in advance. :)

I don't flip in the true sense of the word, since I will sometimes buy for a few weeks then sell to a buyer on forums. And then sometimes I am able to sell my item for 20% profit while still buying more. Working on items that are in high demand, yet have an annoying buy limit are great ideas. People on forums are willing to pay quite a bit extra if you buy an item for a week straight and sell it to them in bulk. And sometimes you get lucky, and can sell it in ge for the same you would get on forums, which resets the buying limit, and let's you buy a ton more than the limit would normally allow. Just for having my offer in for ~10 days, I've made 8m profit for no work, as I never check GE prices lol.

Buy low, sell high. I've also heard repairing Barrows armor at your POH's armor stand is good profit at higher smithing levels.