The way I farm makes just as much as rockdassie's way with speed, it's a different technique but the profits are the same. and I don't use speed. (even though using speed 2 can increase my profit by roughly 1k)
Kuke, maybe you could pm me the technique you use? i have 4 cane farms and have spent hours studying groth and different techniques to make the most out of them.
I think sugarcane is good to start out on, I use RyanJF1's farm and get a lot of money with speed potions and then farm pumpkins while the sugarcane regrow.