From most to least important in my opinion
Position, you can be a rock star farmer but if your farm is in the middle of the Sahara there's nothing you can do. and positioning is the one thing you can do nothing about after you start, think of soil, aspect, climate and most importantly access to customers.
Marketing, yes I feel marketing is more important than any type of growing, plants want to grow, customers do not necessarily want to buy.
Organisation, Planning helps stop mistakes, you'll still make mistakes but hopefully they will show up earlier. for example not ordering 1000 strawberry plants when the field is still a horse pasture (cough)
Knowledge. This comes last, just remember you don't know anything and look up everything you think of and many things you can't!
Also be patient, it won't all happen at once, start small and grow both on area grown, plant types, customers and your expectations.