There are two types of reviews 1. Product Reviews & 2. Seller Reviews.
Product Reviews - These are somewhat important when doing product research. You will want to make sure products you are going to sell have at least 5 reviews and an average 3 star rating or better. This important to make sure you are buying a product that customers like so you don't have to deal with a lot of returns. These are reviews of a product and have nothing to do with you as a seller.
Seller Reviews - These are reviews of you as a seller. These are also not extremely important but you want to shoot for at least 1 review and at least a 90% positive rating. You will get these reviews aromatically as you sell products.
In short, reviews are not very important in this business and that is why you can get sales the first day of going live without any reviews :)
