Is there any information available about how to configure subscriptions/ingenico?

We have created subscription template, product and quotations. However anything further than that seems to be an entirely manual process. It seems that even when a successful payment is made there are manual steps required to manually validate the sales order/invoice and then to create a subscription. Surely this process should be automated in the case of a subscriptions based model.

Hoping someone can help as this is a fundamental blocker to us using Odoo more widely in our business.

Your question is quite confusing because you are mentioning on the one hand "the first card" as if the customer would have several cards recorded in Odoo, and on the other hand you mention a fall back payment method. So, in the case of a failure, do you want to use another card with the same processor or the same card with another processor/payment method?

Generic answer:
If you need to manage recurring payments due to, for example, a recurring membership fee, you should use the Odoo Subscription app. In Odoo Subscription, when a payment charge fails, Odoo will try to charge the card on file once a day every day for 15 days through the payment processor specified on the payment token record. As a note, Odoo Subscription only works with the gateways Ogone/Ingenico and Authorize.net as of v10. There is no mechanism to try another payment token that Odoo would have on file automatically; it is however possible to change that manually in the Settings tab of a subscription. But there is certainly not a mechanism to try to run the card through a different acquirer because Odoo only saves a token, no card data. This means that the token that Odoo knows is the reference of a card data in the vault of a certain gateway. As a side note, it would be wrong to believe that a charge could work through a gateway/processor and not through another one. The reason of a failure is in the vast majority of cases on the customer side (expired card, wrong card number, funds limit exceeded, international card configuration,...).

In conclusion, the fact that the customer receives a notification when a charge fails, with a link to pay (possibly with a different card) and the fact that Odoo Subscription tries every day for 15 days and closes the subscription afterwards automatically should be enough to ensure that you customers will pay their fee if they want to keep benefiting from the service.