Focus on reviewing products that fall within your niche. Then, leveraging the rapport you have created with your audience and your stance as an expert, tell your readers why they would benefit from purchasing the product you are promoting. It is especially effective to compare this product to others in the same category. Most importantly, make sure you are generating detailed, articulate content to improve conversions.
Next, you’ll want to pick a WordPress theme from somewhere like ThemeForest, Elegant Themes or OptimizePress. This is the barebones design of your site, which you can then customize with your own branding, copy, and images. That being said, you don’t want to cheap out. It costs less than $100 to buy a theme that will make your website look professional (and you can upgrade to a completely custom design once you get the business going).