This is how you do it.
<div id="post-body"><!--remove padding tag from post-body-->
<div style="mytext">Lorem ipsum dolar set</div>
<img src="any url">
</div>
In head section or just above this code, add the following code: (as you said, you are using blogger)
<style>
.mytext
{
padding:12px;
}
</style>
Apply "mytext" style to every text you want to have padding.
Another simple solution is don't use blogger. I used it initially but stopped it because of these reasons only. With Blogger, you can't get enough customization and you are under "Google" and dependent on that. If you want to make your blog unique, a much better alternative is to use WordPress which is open source, independent and has more customization.
Though it will be difficult for you to move from blogger to word press but it will help in future. Bloggers/blogspots were used initially but now technology has moved and we have much better alternative. The future of blogger will be dark as everyone is now moving to Word Press (which enjoys the open-source brand). Check this out