Tags: Use of relevant tags is important from the SEO perspective. It helps the search engine track your post based on the tags you use.
1 per day: If you have just started blogging, then writing consistently might take time. So set a target to have 1 post per day that is well researched.
E-commerce bloggers can gradually choose to write curated content from other websites/blogs. That always helps because a buyer will generally not spend much time surfing. He/she will appreciate it if you provide most of what they are looking for.