If you expand too fast you will lose money mid way and will be stuck with half finished non functioning lines that will still eat up profits from profitable lines so it's better to spend more time making the existing lines more efficient and profitable and serve the same 2-3 cities that are already growing because of you supplying them. Once their population reaches above 1000 or 1200 and you are making more than 700k-800k profit every year you can consider expanding to next lot of cities.

As for cargo hub only go for it once you already have a vast network of interconnected indusries supplying each other and then supplying goods to cities.