The reason I ask this, is because it seems like it's common knowledge to pit keywords together for any niche site. So, why is it the likes of keyword tools/researchers are really needed? I personally feel like it's best to just find the keywords that fit with the niche yourself.
Yes absolutely! Keywordtools can tell you about search volume and competition. If you sell Rolex and one million other people do the same it might be a great idea to find a more specific keyword.
Yep dude Make sure your keywords are relevant to your niche Focus more on writing something good, then edit it and include a few keywords or buzzwords.