What SEO tool should a Newbie buy?

Hi there people.

As you can see in the title, I am interested in buying a safe and powerful SEO tool. The money really doesn't matter I have enough. I have been building backlinks manually just to see if I am good at this and I got some nice results... The website is 2 months old (wordpress) and I have managed to rank it in 1st page.

Thanks in advance.