What variables can I use?

Referon can accept any variables in your trackers. 
The most common 9 variables are found in Reports - General as separate columns:
var1
var2
var3
var4
var5
subid
pubid
clickid
click_id
However, if you are using anything outside of these, such as ‘webmasterid’, this can be collected in the ‘other’ the 10th column in dynamic variables group.
Note: if you are using postbacks, ensure the variable matches to your callback url requirements.