This season was just less focused around Betty. Weiner says there'll be more Betty next season. And that probably means more Sally (possibly even Bobby character development!). This season was about SCDP starting to take off. They got more notable clients and money started coming in at the end. In season four, SCDP lost Lucky Strike and a couple other clients from the ripple.
And the other main plot was the personal life of SCDP (obviously). Don and Megan being newlyweds, Pete living in the suburbs, Roger getting divorced, Peggy leaving due to a lack of acknowledgement/respect from Don, and Lane's tax problem from England.
--
"Coinflip is sacred."