What are the requirements for going from the Beta to Alpha insider ring?

Not all Insiders have access to not requiring gold for f2p games at the moment.Only Alpha/Alpha skip ahead & Beta rings are testing it.If you are not in any of those rings then you will still need a gold sub at the moment.

Are you in a Insider preview ring?

If so, which ring. ASA, Alpha Beta or Omega?

You need to either be in the uk or us and be an xbox insider on ring beta, alpha or alpha skip ahead.

Hi, I tried to private message you but it didn't work.

You have to be in the insider preview to download the avatar beta app. It works on the original Xbox One, the Xbox One S and Xbox One X. It is not rolled out by console model but by which Insider Preview ring you are in. It has now been rolled out to all
rings.

Insider Preview has Alpha Skip Ahead, Alpha, Beta, Delta and Omega rings. Alpha Skip Ahead and Alpha are invite only from the development team. You can use any Xbox One family of console in any of the rings.

Seems you have to be invited to join the Alpha ring

https://support.xbox.com/en-US/xbox-one/console/xbox-insider-program

The current Xbox One Update Preview rings are:

• Alpha – Open on an “invite only” basis and receives updates at the earliest point in the preview window.
• Beta – Open to Xbox Insiders with a Program tenure of 3 or more months and an Xbox Insider XP Level of 5 or higher. This ring receives updates shortly after Alpha.
• Delta – Open to any Xbox Insider with a tenure of 1 or more months that has reached Xbox Insider Level 2 or higher. Depending on certain edge cases where further attention is required from Alpha or Beta rings, Delta Insiders may receive
  system updates before Beta, though this is not a common scenario. Additionally, while early system updates are not guaranteed across the Delta ring, all Delta Insiders will receive the update prior to GA.
• Omega – Open to anyone and receives system updates shortly before the GA (General Availability) release.