Diversity means having a range of different sources pointing to your website. This leaves less of a footprint and looks extremely natural to search engines. This is where services such as link wheels and link pyramids come in handy.
If you are simply planning to have a simple link building strategy where all links point directly to your money site then you should look into purchasing web2.0 and other highly regarded links such as EDU and GOV links. These types of links are able to pass huge amount of link juice to your main website without the risk of penalties.