Welcome to the Babble!
For a better experience here, you may want to check out our Guidelines and Forum Help in the top horizontal menu and at least listen to the video (better to read as well). You will find some interesting tips and information that you will want to know, such as signature requirements, etc.
Glad to have you join the forum, a great place to learn and share.
As for your questions:
First, if you need to use a free theme, the new twenty-fourteen theme that comes with WordPress is excellent. It has lots of options. With a lot of free themes you are taking some risk, so when you are unfamiliar with working online it is better to be safe and stay with the tried and true. And that is an excellent choice.
If you do have a little cash, for 84.95 you can get the Genesis theme (which many of us think is the best) with the Prose child theme (you use a child theme of which they offer many). Prose is one of their best choices. You can look at all of them but be sure to use the middle drop down box for features and choose media responsive. That is essential with any theme you use now; it means it will work with all sorts of devices and half of our users now use iphone, kindle, ...
Second, find a good source for learning how to use the program. The best I have found is on WPBeginner. After you sign up for their newsletter, when you click on the video button it will give you a list of 23 (as of today, they keep adding) videos that give excellent, up to date, instructions for using WordPress.
Third, stay in touch with the Babble. There are a lot of great folks here ready to help you with any problems.