Blogging. It's one of those things that at no matter what stage you're at or how long you've been doing it for, there's more than likely so many areas that you wish you could invest in to better different aspects of your blog. Whilst investing money into your blog can certainly help to improve these areas, I know of many great blogs which have gotten by with barely shifting a penny, and so it may not be essential for everyone.
Most importantly, I personally feel that if you're a newbie into the blogging world or are perhaps considering the possibility of it right now, don't feel the need to invest financially at an instant. Blogging is something that takes up a considerable amount of time and because of that simple factor alone I see many people giving it up after a few months. The number of abandoned blogs on the Internet is probably extortionate! So just a personal recommendation, don't invest in something that you're not certain you'll love further down the line, and don't feel the need to invest at any point if you really don't want to - you can still create a successful blog without any financial investment.