The best way to accomplish this is to create a new Group.
Call it something like “New Sign Ups”. Some brands will also add some notes to the Group details page, in the "Description" cell, like a date that this introductory offering was activated.
Then, under Settings>Customers, select that "New Sign Ups" group so that anyone who creates a new account goes directly into this Group.
Back on the Group details page for the New Sign Ups group, build their allocation:
Set it as Active, with a long ranging set of dates, from now until the end of the year perhaps.
Fill in the Messaging section so these new customers realize they are being offered a "special allocation for new sign ups"...."For a limited time we are offering all new sign ups access to a small selection of wines from our previous release...."
Load the SKUs you want to offer to these customers, along with quantities.
Decide if you want to set a cart minimum for checkout? For example, if you are offering only one bottle of three different wines, a customer has to at least get two of the selections. Not required, but an option if you so choose.
Save Changes.
With that, anyone who creates a new account via the website will land on their main profile page, and there will be a button pointing them to that allocation page with the chance to buy right away.
On the Settings>Content page, there is a text block called, "Active Offering Message". This text appears on a customer account page when they are in a Group that has an offering currently available. With this, you can highlight that "by clicking the button below", they will be taken to a special new customer introductory offering.
You could also add some verbiage to the "Customer Welcome Message Web" email on the Settings>Email page. This is the email that goes out to a new customer after they sign up via the website. Your verbiage can include something along the lines of, "In case you missed it, log back into your new account and there is currently an offering available to buy wines from our previous release."
Then, perhaps once a month, you go into the New Sign Ups group, click the top check box on the left to select all the customers, click the “Choose an Action” drop down menu, and select the “Move to” option. That would get all the new sign ups, say from the month of August, out of the New Sign Ups group and into your main group (Mailing List, Tier 1, etc).
You could be more selective and move the people that bought wines from this introductory offering into a higher level tier of your groups and the people that didn't buy go into a Waiting List type of group or low level tier. Lots of options for how you want to manage those new customers who buy or don't buy.