A: Hi Name Game, thanks for the question. I'm no authority on the subject - I blog on a small set of niche topics for personal reasons and don't ever expect to acquirea big audience - but I'll give you my two cents for what it's worth:
- If you're blogging in hopes of making money, don't. Very, very few bloggers make anything approximating a living wage doing so, and the window for developing a new "must-read" blog on a mainstream topic is all but closed.
- If you aren't doing it for the money but still want to acquire a big audience, weekly posts aren't going to cut it. Pick a narrow field - the business of baseball isn't bad - and bring fresh, original ideas to the topic, with an emphasis on breaking news, every day.
- From an SEO perspective, I'm not sure having yor own domain makes a big difference, unless that domain corresponds to a common search term in your topic area. It might be nice to own a domain to make it easy for readers to find you, and to make the brand portable if you want to change blogging platforms (plus it's cheap), so if you find a good URL go ahead, but it's not a make-or-break.