You'll still need a way to know where you got the advance from.

• Access to Settings→Leads→Sources and add a source according to your needs.
• To configure the default Leads source, go to Settings→ Configuration→ Leads and choose Default source.

You can assign a source per lead and you will know where your leads are coming from and where you have the most leads converted to customers when generating the report.
The default lead source is used for automatically fill the source field when creating a new lead . Every time you add a new lead, that source will be automatically selected.