How should I store a simple, time dependent, repetitive data type in drupal Im interested in collecting simple data series over time with Drupal. for instance, lets say a user wants to input a monetary amount the spend on a given item each day, and then track that over time. It seams like overkill to log the information as a node, or even an entity for that matter. What is a good way to store data of this nature?
I think Webform is what you are looking for. You make a form that user(s) can fill in and submit. 

You can track the submissions over time, export them etc. There are lots of features you can do with webforms.

This is not a complete how-to for your question but you can take it as a start point. This way you don't create a node for each submission, but the form itself will be a node of type Webform.