I'm also currently tackling the one million scenario after seeing a few let's plays about it.
Looks like I am taking a very similar route. My sim is also starting out in Henford on Bagley and doing gardening. My sim is focusing on a dragon fruit farm because they have a good selling price. The only plant I won't let her use is the money tree. She is about to double her number of dragon fruit plants to 30 plants. When she has nothing to do, I have her paint and sell the paintings on plopsy. So far I am two weeks in and so far have nearly 44.000 on my sims bank account. But she also had to built a micro home because she started out on an empty plot of land. She is living off the grid with the simple living challenge just to make it a little bit more interesting. I also got her a chicken, a cow and a llama but is turning out to be very much work so she might have to scale down on the farm animals.