Well its tough to answer this as it really depends on the type of business you're in, because certain marketing strategies only work for specific businesses.

In terms of immediate impact to your business, then PPC or Social Media marketing are by far the quickest way to get your business up and running. The key to launching a successful PPC/SMM campaign is the following:

1.) Have an expert who knows/understands the customer funnel
2.) Focus on bringing your CPC down as much as possible, which will allow your budget to last longer.
3.) Do an in depth research of upward and downward keyword trends and try to nail down key areas that you can maximize

I own a digital agency called Noticed based in Philadelphia, PA. Our agency has had extremely successful results with our clients seeing an increase of traffic and sales of 40%-300%. within the first year.

I hope this helps.