I have a campaign where each week/month keywords seem to go from profitable to not profitable. It just varies so much. What time frame would you look at to determine if a keyword is profitable or not? or what kind of volume? It's hard to determine if I should keep a KW or not, when last month it did well, now this month it's not...
search on Google see total About ..... results after than use Google key words tool to find monthly local and global searches....
Use Google Adwords: https://adwords.google.com/o/Targeting/Explorer?__u=1000000000&__c=1000000000&ideaRequestType=KEYWORD_IDEAS#search.none
No matter the tools you use, experience; learning from your mistake will be your best guide. Do not blow a huge budget but, experiment and if you can afford to try 2-3 months and see how thing goes and change your strategy on the way.