Can I start a mathematics blog with Blogger. If Yes what are templates I need and How to write mathematical equation in my blog
I don't think it is a good idea. You can use any good template for blogger. Templates doesn't matter much. You can use WordPress plugins to write eqautions
Can you give a little bit more details, please? Like expected audience, school or university level? Which type of content?
Yes, Jess_Shpek is right. That will include some investments there.
If you want to start a serious blog, you'll need to spend a few dollars on a good theme. Be sure to consider using wordpress elearning themes https://www.templatemonster.com/category/education-wordpress-themes/ . Any of them will work fine for your mathematics blog.
You can certainly do on Blogger, but I think it's wise to go with wordpress if you can invest a little.