Google Blogger offers a lot of useful and helpful widgets which you can easily add to your blog.
All you need to do is click on the "add a gadget" link and you'll be taken to a page with all the free gadgets that you can make use of.
Choose the one that you want and then click on the plus button and the gadget will automatically be added to your blog.
You can edit these widgets a little bit such as by deciding on whether you want your labels list to appear in list format or as a cloud.
However, if you want to edit said gadgets further such as changing font colors and the like, you won't be able to easily do that without going to your blog's HTML or CSS.
Furthermore, while Blogger has numerous widgets that you can choose from, it doesn't offer everything.
If you're looking for more gadgets, you will have to search for the codes yourself and add them to your blog.
For example, Blogger offers the Popular Posts widget but it doesn't have a Recent Posts one.
Blogger has the +1 Button gadget and even a Google+ Followers one but it doesn't offer anything about Twitter, Facebook, Pinterest and other such web sites.