Confusion Concerning Ideal Outdoor Soil Mix

My plan this year is to germinate from excellent seed stock (possibly Canna Sutra or AK-47), start my plants indoors, and transplant to the ground when the threat of frost is gone (I live in the deep southeast). My experience in the past has been to grow Northern Lights clones outdoors (some in large buckets), and I have had reasonable success. This time around I want to limit my grow to two only plants and I want to replace the crappy native soil with the best mixture I can come up with. I have researched this site and have found many excellent recommendations, but none pertain exactly to my specific situation.

Thus far I've run across recommendations such as these: "dig a hole two feet wide and three feet deep;" "use 100 % Fox Farm Ocean Forest start to finish;" "don't use Fox Farm in the beginning because it's too hot;" "use 2 parts Pro-Mix, 1 part vermiculite, 2.5 cups of lime pellets, 1 cup of North Country Pro-Gro (5-3-4) supplement; and 1/4 cup worm casings per 5 gallon container." "Dig a hole and fill it with 2 cubic meters of high quality organic potting mix."

I've priced Fox Farm Ocean Forest in my area and the best price is $20 for 1.5 cu.ft. I'm not sure how much of it would take to fill one 2 ft. x 3 ft. hole but my guess is at least 3 bags or $60. If this is what I need to do, then so be it. But I had hoped to run across someone on this forum who had developed a good recommendation for a standard outdoor hole. I would certainly appreciate any input that you guys can offer.

thanks