Individual automation rules work well for a notification or a single task, but this process has several branches and must pause while people make decisions. A workflow can carry the request through those stages and return it when someone asks for changes. Before building it, read about Bitrix24 workflow automation here: http://roboteka24.com/blog/bitrix24-workflow-automation-guide/ . Connect the workflow to the purchase request card and have every decision written back to the same card. Test it with one department first and review the workflow log whenever a request stops unexpectedly.