Hi, this is Tim here,
it is important to add good post to your blog and stick to relevancy to your topics to get targeted visitors.

Am i right ?

Yes you are right. good and unique as well. Also you will get targeted traffic thanks to your keywords in your post/s from SEs.

Readers usually subscribe to your blog because they like the topic. Try to keep your posts related to the general theme/topic of your blog. If you wonder away from it, you could lose readers.

exactly... interesting, unique and fresh really makes a difference.. and also what SEs really like...

This seems like pretty basic stuff...

Yes, you have to stick to your site's theme... Having fresh and quality contents will definitely attract more visitors to stay longer and come back again to your blog....

make it relevant dude! Users will love your site same as google if you do that!