Although there is currently no formal support for sending a 'Success' email during an Orchestration, the job can be done using a 'SQL' Movement.
Simply copy-and-paste the following code into a new 'SQL' Movement, added to your Orchestration, changing the message parameter values as appropriate.
DECLARE @EmailTo nvarchar(max)
DECLARE @EmailFrom nvarchar(max)
DECLARE @EmailSubject nvarchar(max)
DECLARE @EmailBody nvarchar(max)
SET @EmailTo = 'example@example.com'
SET @EmailFrom = 'example@example.com'
SET @EmailSubject = 'Event Complete'
SET @EmailBody = 'The Event Completed'
INSERT INTO [DataAcademy5.6].[dbo].[__tblSystemEmail]
([EmailTo],[EmailSubject],[EmailBody],[FormatHtml],[PostDate],[EmailFrom])
VALUES (@EmailTo,@EmailSubject,@EmailBody,0,getdate(),@EmailFrom)