Modelling business data


I have a strong history in modelling chemical data and other scientific data. I have a data set that I'm working with and I want to take some advice on how to determine the relationships between variables.

Basically, the data is taken over time (variable 1) and I have data for media spend (variable 2) and sales (variable 3). Let's assume I have two other variables too (4,5).

I want to look at the relationship between spend and sales and the other factors. Simple linear regression doesn't really apply because of the time scale - i.e. spend starts early and sales lasts longer (for example). If we don't consider all of the extraneous factors that one must consider and simply think about what method to use, how is the best way to model this? Some form of Time Series based regression?