I would choose ground over 50L pot for sure. Work on/assess capacity for drainage first and amend if necessary with peat moss, pearlite, coco choir, sand, pumice, composted straw, ect. I like pumice for pure drainage but organic mater is very important as well, so some compost and or peat moss, coco choir is probably equally important if not more depending on your soils capacity for drainage. It would be good to get an idea of your soils ph as well, cannabis prefers slightly acidic conditions.
As far as organic nutrients that depends on what approach to organic you are going for, personally I am sold on the concept of feeding the soil not the plant. This method focuses on the microbial colonies in the soil and their function in essentially digesting raw organic materials into forms of nutrients that the plants can then use more effectively. You feed the soil microbes and the microbes feed the plants, because of this my favorite nutrient is compost.
If using bottled nutrients pay close attention to labels, a ton of nutrient lines that many people assume are organic because of how they advertise themselves are in fact only "natural" or "organic based", and contain salts/chemicals the are harmful to the microbial life in your soil. Single ingredient fertilizers are a good way to go if possible like, alfalfa meal, crab meal, insect frass, ect.
Foggy conditions start around mid October for me as well, most of the time it is not an issue, but if you live in a place that gets a lot of rain towards the end it can cause problems. A cheap hoop house can help in that regard, and if it's really wet/humid you can run fans and dehumidifiers, however depending on your climate that may not be necessary.
