Buy a premium template only after you have 20 published posts and are making at least $5/month from ads or affiliate links. At that point, the $15–$40 investment will pay for itself in higher RPMs (revenue per thousand views).
Some "premium" sellers cram in too many features. One template I tested had a built-in social share counter that called 8 external APIs—slowing the site to a crawl. Always test the demo on Google PageSpeed before buying.
This is the hidden gold. Premium templates come with proper Schema.org markup (Article, BreadcrumbList). Two weeks after installing, three of my old posts appeared as "Rich Results" (with images and star ratings) in Google Search.
When I broke my sidebar trying to add a Mailchimp form, I emailed their support. They replied in 6 hours with a custom CSS fix. You will never get that with a free template. The Bad (Read this before buying) 1. The learning curve is real Because premium templates have 200+ customization options, it is overwhelming at first. I spent the first two hours just figuring out how to turn off the "Breaking News" ticker. If you want "simple," stick with the official Blogger default themes.