Answer:
First focus should be on product. As all other decisions depend on type of product or service that you are offering. For product you need to focus on "Unique preposition". How your product is different from competitors. Once product is finalized with its target market and research on potential customer and their needs, next focus should be on price. Price needs to be fixed by keeping in mind these factors
1) Competing product price
2) buying power of potential customer
3) Pricing strategy (Skimming or penetration)
Then focus should be on place, where this product will be sold.
Then with these information you can promote your product to potential customers. As your promotion strategy will need all above information for it to be effective.