Backlink Question

Hi Guys,

I have heard that if you want to rank for your main keyword phrase which is obviously the index page of your site then it's best to use at least 3 different variations of the keyword when building backlinks so it doesn't look spammy.

So if my main keyword phrase was "Dog Training" and that was my URL, meta tags, title of the main post, keywords within the main post etc....I would use the phrase "Dog Training" as the anchor text link when creating backlinks, but also I should then have a few others so it's not spammy...like "Dog training lessons", "dog training course"....etc

So my question is should the other keywords also be embedded in that main post. So if the index page of my site is optimized for the keyword" Dog training" should I then also place "Dog training lessons", "dog training course" into the main post as well, or doesn't it matter?

Also should these additional keyword phrases be actual phrases people search for and have a decent amount of traffic associated to them, or doesn't that matter either.....is it just important to have a variation of my main keyword phrase when creating anchor text backlinks so it doesn't look spammy to Google?

Any advice would be appreaciated.

thanks.