Animenbo

This site will  help you make a good related posts.
http://helplogger.blogspot.jp/2016/09/new-related-posts-widget-for-blogger.html

For SEO, breadcrumps navigation is very important. In this article, he explains how to add it in Blogger.
https://allbloggingtips.com/how-to-add-stylish-breadcrumbs-navigation-in-blogger/

This is CSS menu bars for Blogger. A lot of designs and easy set up!
http://www.bloggertrix.com/p/css-menu-bars.html

The menu will be in the center
http://www.designerblogs.com/adding-pages-to-your-blog/

Easy design labels
https://allinworld99.blogspot.jp/2015/01/blogger-label-widget-blogger-label.html
http://www.bloggerspice.com/2015/01/CSS-custom-label-widget-for-Blogger-Blog.html

Blogger Updated Dates
https://p--q.blogspot.jp/2013/08/blogger9.html
http://blog2.k05.biz/2013/05/blogger-last-modified.html

Appearing data header
http://blog.saku-lab.net/2012/12/blogger.html

Add gadget on Blogger main
http://sekirarablog.blogspot.jp/2013/04/blog-post_5230.html