I am a beginner to Network/Graph Analysis. I have data in the following format:

**Customer | CustomerSpend**

Anna                    $10

Bob                     $30

Charlie                 $50

**Customer1 | Customer2 | RelationshipStrength | ZipCode**

Anna          Bob            5                      11111  

Bob           Charlie        10                     22222

- I want to visualize and conduct some analysis on the data set (which groups spend most, which zipcodes spend most, etc.). 
- I am thinking of using NodeXL or igraph (in R) to get started. 
- I also want to brush up on graph theory to understand the various metrics I could look at.

What resources can I leverage to get started?