Starting on Amazon is easy, however starting and competing with sellers already having tons of reviews on their listing is difficult. 

So its a chicken and egg problem. To get more orders you need to have seller ratings. To get more seller ratings you need to have more orders. 

You can start getting orders by selling some niche products or if your budget allows you can start with Amazon ads. 

One thing that many of the people ignore is the chances of getting a reviews on your store. Off course if you are able to ship it faster and you have better products your chances are going to increase of getting a good feedback. 
However you need to reach your customers in order to get the positive reviews. And one of the best way to achieve is to send SMS & Email notifications after the delivery has been completed and asking them to leave the feedback. 

For this you have to use some Shipping Notifications tools like Shipway.in and customize the shipment delivered templates and place this link https://www.amazon.in/hz/feedback/ to get more feedbacks. 
When the link is getting delivered on the text notifications customers are 50% more likely to leave feedback for you.