Im not really a fan of FF soil as it's pretty pricey for what it is. I use pro mix HP(peat moss mixed with perlite and a few other goodies. Considered hydroponic though as it's soilless.) I use the Fox farms trio, and for flowering I use the trio(minimal big grow/nitrogen) open sesame and beastie bloomz. I can not stress enough that beastie bloomz is the shit. I have not tried a bulker that can honestly surpass this for my environment. I also just started to use terpinator as recommended by a few others and have seen good success and some good flavors in the wax I make.
when you should start using nutrients and how much water is hard to say over the net. All plants are different. You can have 2 of the same plants of the same strain from the same breeder, but they could be different phenos and act differently. But generally 2 weeks to 1 month in is about how long the soil will last you... But once again so many variants. Just make sure the soil stays moist. Poke your finger 1 inch into the soil and see if its moist. If it is your good on water
For transplanting IMO you only want to have to transplant once. Grow it out as big as it can in a solo cup, then transplant it into your final pot.
My grow with Fox Farms products. I use 7 gallon smart pots.