I would like to build a system for purchasig system/ERP

Hi everyone ! I want to build a system that can easily to make my company staff to doing job. I search mostly ERP that no one is suitable for my company.
I have totally no idea how to starting learning it and build it, and which language is more suitable for this?
I have own idea and working flow to suitable my company.
I also want to make it web-based to let other branch login and check.