#1: Product images that are professional and communicate trust
Consistency is a big factor
#2: Effective description of the product that is being sold
#3: Boosters of consumer trust and reassurance of consumer purchase
Keep in mind in customer perspective, they never heard about your brand before, this is first time they interacting with you as merchant, this can be very scary experience even if they are impulsive buyers, and you already capture their interest with your ads, anything you can do to reassure they will go very long way.
Something I do on every product page is including sizing chart, return and exchange policy so that consumers can be confident that they are not about to get scammed, and there is full transparency in their post-purchase experience and their customer service that we are going to offer.