As this is your first time, yes I would get the soil. Keep the coco for later - don't worry about wasting it. The soil can help balance a lot of first time mistakes. With the coco, the mistakes are much easier to make. If it is possible for you where you live to buy pre mixed super soil, I would do that. That is a specially prepared soil that has all of your nutrients already in it. All you have to do is water and wait. Some of the guys growing seeds and strains for TGA seeds use only super soil for their incredible cup winning grows.