Plugins are additional code that can add something to your site. For example, the Social buttons you see in most articles are plugins :)
With this WA advises you to now use more than5, but this is only a suggestion, most of the guys and gals here making money have double that.
I don't make any income yet, but I have already gotten about 7-9 plugins for my site.
This is fine as long as the plugin doesn't slow down your sites load up time because you can actually lose traffic just by your site taking too long to load.
I would suggest making a test site and downloading the plugins there to test them out before putting them onto your main site.
Site trust
Site trust tells you how long you have been around basically. The description says, "As your website matures, the search engines will trust it more." Now that doesn't mean that Google will trust your site if it's been up for 5 months with no content added to it.
The trust comes from how many times you blog, how much you engage with your audience in your comments.
As you can see it''s been a month since I started my new site earning paychecks and my site trust is still at 0%.
I only have 5 articles and 5 pages so I assume that as I get closer to the 10 blog mark then I will see that go up.