With Google and other major search engines now requiring you to have SSL (https) enabled on your site, you absolutely need an SSL certificate. If you don't want to pay for a commercial SSL certificate, there are free alternatives available that won't cost you a single penny.
Cloudflare is offers a flexible SSL free of charge for all your domains as long as the DNS is managed by Cloudflare. You can easily enable their free SSL with the click of a button and it renews automatically. The only drawback is that you need to transfer your DNS to cloudflare however cloudflare offers so many advantages that it is worth the effort.
Let's Encrypt is a non-profit organisation that issues free SSL certificates for anyone requesting it. It requires some advanced technical skills to generate the SSL certificate but once you have done it, you can easily generate a certificate for any domains you have. You can install Certbot (a bot that allows anyone to use Let's Encrypt) and very easily issue certificates for your domain via command-line interface.