I could talk about this topic for ever and ever and ever. I'll try to be brief
Wordpress and Blogger both have excellent spam control - so if you're getting spam in your comments, there's something not configured right. The spam should be filling up your spam folder only. Wordpress uses Akismet so I'd check out your settings for that. I don't use free wordpress anymore so I can't remember what this looks like on the free side, but I can check into it tonight when I'm at home if you want me to.
If you're using free Wordpress, you don't have access to plugins created by anyone but wordpress staff. If you end up moving to Wordpress.org and self hosting your site, you'll hvae access to a HUGE library of plugins, and I can give you some good recommendations as well as sites with good plugin reviews.
Deciding what you need on your blog is easy - go check out all the blogs you really love to read and see what they have. Then copy what they do. You're not cheating
Most blogs have similar, if not the exact same, layout and information on them. People come to expect this. People know that there should be a short blurb about the blogger in one of the sidebars. THey know that there should be a FriendConnect box there too. Here are a few tips though:
1) Make sure your name is in the little profile box on the sidebar, even if it is other places in your blog, this is where people go to look at who you are and how to spell your name.
2) Make sure your email address is there too.
3) Include easy, graphical links to your rss feed (so people can add you to their feed readers) Twitter, Facebook, Google+ and/or whatever other social sites they can find you at.
4) Whatever is in the top half of your blog that shows up on a normal monitor screen without scrolling is the most important information on your blog. It's the snap shot people will look at to decide if they are going to stay or not. If there is any information in this snapshot that you feel is unnecessary, move it down.
5) I see your blog is a black background with white text. Take caution with this. For quick updates it's no big deal, but studies show that people have a hard time reading white text on black background - it puts a lot of strain on the eye and some readers won't come back if it's too tough to read. The ideal is usually black lettering on a light background, but the colors are up for debate so long as it's dark writing on light background. Stay away from yellow as it also causes more eye strain than other colors.
6) Don't worry too much about how your blog looks, concentrate on content and developing a habitual schedule. Your blog will morph as you do. I've gone through many designs and I will probably go through many more.
7) Useful Widgets: Calendar and Archives. Most people don't care about recent comments but if you have access to a widget that shows your most popular posts, that can be very useful.
8) Keep it clean. It can be tempting to fill up your sidebars with awards and buttons and other ephemera, but don't. The more cluttered the harder it is to read. Put only the most relevant and useful to your readers and keep it up to date. Put other stuff on a different page.
9) There aren't any rules. These are just guidelines and ideas, but anything goes. Really it does. When I give advice about blogs and when I build them for people, I always encourage people to do things they like about other blogs. THinking as a reader is the best way to make YOUR readers happy.
I have a series on my blog called College of Blogging where there's lots of good info, if you're interested.