You don’t want to “keyword stuff” and cram your core keyword and every possible variation of it into your alt attribute. In fact, if it doesn’t fit naturally into the description, don’t include your target keyword here at all. Just be sure not to skip the alt attribute, and try to give a thorough, accurate description of the image (imagine you’re describing it to someone who can’t see it – that’s what it’s there for!).
Gaining Google's trust doesn't happen overnight. It takes time. Think about building up your relationship with anyone. The longer you know that person, the more likely that trust will solidify. So, the reasoning is, that if Google just met you, it's going to have a hard time trusting you. If you want Google to trust you, you have to get other people that Google already trusts, to vouch for you. This is also known as link-building.
Finally, it’s critical you spend time and resources on your business’s website design. When these aforementioned customers find your website, they’ll likely feel deterred from trusting your brand and purchasing your product if they find your site confusing or unhelpful. For this reason, it’s important you take the time to create a user-friendly (and mobile-friendly) website.
Content is king. Your content needs to be written so that it provides value to your audience. It should be a mix of long and short posts on your blog or website. You should not try to “keyphrase stuff” (mentioning a keyphrase over and over again to try and attract search engines) as this gets penalized by search engines now. However, your text should contain the most important keyphrases at least once and ideally two to three times—ideally, it should appear in your title. However, readability and value are much more important than keyword positioning today.