This applies to pretty much anything and everything you do in life, not just blogging. If you plan on building a successful blog then you must always be on the lookout for ways to improve it for your site readers. Don't think for a second that you will learn enough to get your blog up and slap some ads on it and off to the races you go with a truck full of money. You must give people a reason to want to come back and visit your blog. There are a million different ways to improve your blog and it could be done with small things like adding a poll or a video. Another way to look at it is that a lot of little things add up to a big thing. I'm always looking for ways to improve my sites and my own computer knowledge and skills.
If you are just starting out then I wouldn't worry about trying to add all kinds of stuff right now. The biggest thing you need to be doing is creating some content for your new blog and getting comfortable in the blogosphere, but keep this in mind for the future. A good way to get ideas for stuff to add to your site is by going and looking at other sites like yours and seeing what they have on their site. You can also ask your readers for suggestions about what they would like to see on your site.