Soil preparation is #1. In a first year plant probably more important than the amount of light. Proper moisture is obviously also very important, but the soil is #1. When the rhizomes are just planted, there is so little root area that in order to get the fast growth needed to have a good harvest the first year, it's the first month or so that sets the stage for the huge plants by harvest time. Easiest way to have great soil is to compost your own and then till the soil with the compost. I save all of my kitchen scraps and paper and chuck it all on the dirt in my backyard. I keep it moist (cover during storms) and add to it continuously). It never gets to the finished compost look of store bought stuff but I prefer it that way. The partially composted material is like a time release formula so I know there is always nutrients at the root level.
After a month or 3 I then put a healthy 2-3" layer of compost around the perimeter of the bines. This keeps the soil dry right around the bines, but allows for nutrients to leech into the soil when I water/rains.
Following that procedure has resulted in a VERY nice 1st year cascade crop. I had limited my teepee support to only ~8' since I thought it wouldn't grow much and I regret that decision as I could have easily met the 12-15' height and then some. I'm sure it hurt my harvest a bit, but I should still get a couple batches worth.