I want few advise from you experts.

I am learning web designing. and just designed some magento themes manually but still i want to learn theme structure properly. When i was surfing on net i have come a cross few theme generators. Would it did best practice to utilize a generator from the code enhancement and seo perspective?

As I know, YES. It 's better than you do it manually.

Definitely, you can use a theme design generator. I am using TemplateToaster from long time without any hassles. Code is optimized and bootstrap is also supported.

I highly recommend you use theme generator to fix the unknown problem. They 've already done many things for us.