You say you don't know how to build links - if you mean this literally, do not buy SB yet. Learn about links, where to build links, link types etc before you purchase any software.
Automated software is designed to make all jobs/tasks for SEO purposes quicker/easier, and is not an answer to replace any link building method IMO. SB has many uses - people use it to hit lots of backlinks, although this isn't it's only purpose, and isn't always the best way to use the program.
You don't need software to build links, and I am sure there are many people on this forum who don't own a copy of Xrumer/SB and rank their sites on the first page.
If you know about SEO and building backlinks, then SB will help you speed this process up, my advice is just don't buy any bot or software thinking it will be the holy grail of building links and ranking your sites - that comes from experience and knowledge.
Hope that helps