The minimum amount for a single offer of funding is $150 USD or the equivalent in other currencies.
For more information on margin funding, please view: What is Margin Funding?
When using the funding auto-renew feature, the minimum amount for one offer is a funding wallet balance equivalent to $150 USD for the currency you will be providing. If activated, auto-renew will automatically offer the available funds in your funding wallet.
If you have any inquiries, please feel free to contact Bitfinex Support, we are happy to help!