I am researching ways to Integrate our External System (Database) with Salesforce. 
Salesforce Connect/ Lightning Connect would do exactly what we want but its far too expensive. 
I don't want to store data into salesforce. I want to only send requests to External System, and display the response in Salesforce. 

Can someone please point me to resources or  guide how I would create go about doing webservice callouts from salesforce to external system? 
Thanks you !!