Setup and customize a open source BI tool

Hello, I am looking for a setting up a good open source BI tool (available in market) which can be customized for the Retail industry needs. Our Retail division operates with multiple stores under multiple names/formats. Each format has separate DB (Data comes from POS). All of these DBs are stored in SQL server. We need set of reports specifically for each formats and set of reports that have an overview of all the formats in one single glance. I need someone to suggest me the best open source BI tool that can be used for my requirement. And support us to setup and host the BI tool and also need support to customize, create and train us creating the reports. I have attached a comprehensive set of report needs that may be required for our organization. Please note, initially we will need only few most important/primary reports from this set (which will be prioritized shortly). Later we will go for other secondary reports and so on. We will also need you to train us in creating the reports and dashboards so that we will be able to create our own reports and dashboards. [Removed for encouraging offsite communication which is against our Terms and Conditions -Section 13:Communication With Other Users] Looking forward for a quick response! Regards Poornima Vasudevan IT Manager Khimji Ramdas - Retail (Khimji's Mart LLC) [Removed for encouraging offsite communication which is against our Terms and Conditions -Section 13:Communication With Other Users]