Also, LL can make in future LSL script for group UUID gifts?

[KennyChidorie]

Some rent locations don't have settings for any groups.

[Amethyst Jetaime]

You need to create your own group if you want to use a group for your customers and give free gifts.  The land does not need to be deeded to the group, the prim containing the objects just needs to be set to your group.

Alternatively you can use a subscription service instead of a group.  The advantage is that customers can join this without having group space available.  A subscription service will allow you to send out messages and items to you subsciption group.  Subscription services generally charge a monthly fee depending on the number of group members.  Some will allow free use until your group reaches a certain size, while other's charge you if you have one member.  You can script your own too if you have a server.

Some merchants use both methods.

To send a gift, the item must be in the prims contents, in the case of an inworld group gift giver or the server of a subscription group you use to send the gift to all members.  If you use a regular SL group the gift must be attached to a group notice. 

 

[KarenMichelle Lane]

Amethyst's answer is spot on.

Giving you some background based on your initial question of: "Some rent locations don't have settings for any groups."

That is correct in a limited sense. As a merchant, you will find that in-world you can either lease a parcel or you can lease prims.

This is not anything that Linden Lab is responsible for.

Option 1 - Landlord Managed Store Fronts in a Mall Setting

When you lease prims in a mall store front the landlord usually had a group set aside for merchants to be a member of. This allows you to rez your various vendor sales boards and supporting demos and showcase objects. The prims come from a pool shared by all merchants in the mall group. This landlord will usually have a scripted meter that reports the prim usage on a per/merchant basis to verify that each is only using up to the allotted number contracted for. Security is the responsibility of the landlord in this scenario.

If you have a group for your Product Line then you may have your customers become members so that you may send them notices & offerings from time to time.

Mind you, the landlords Mall Land Group will determine the music your customer hears and whether they may rez objects [this is usually forbidden in this type of leasing for security and fraud reasons.] Some Mall owners provide a smallish area as a dressing room that has been cut from the other mall area. This dressing area will have limited prims and will have auto-return set to a reasonable value [10 minutes] like a sandbox does to have the area self clean itself.

Option 2 - Store Owner Managed Parcel

You may also purchase a parcel on a mainland region or on a private estate region. This method allocates the number of prims you may rez based on the total prims supported by that parcel's size. When leasing a parcel is is wise to create your own group for your store and deed the parcel to it. This allows you to manage the security settings on the land that your store sits upon.

If you have a Store group for your Product Line then you may have your customers become members so that you may send them notices & offerings from time to time. This group will also control what your customers may do on your parcel as well. This allows you to control the music they hear as well as whether they may rez objects as well [You might allow this if you offer a dressing room on premises].

I think that covers what I wanted to share...

 

As Amethyst's was pointing out, subscription based groups allow you to send out gifts to your membership from the comfort of a webpage in most cases. All you need to do it have that gift in the "server" object/prim when scheduling the Message + attachment. I personally use HippoGROUPs for this service for my customers. There are many other subscription services out there to choose from.