High-level promotion materials (4 and 5 star) are rare by design but there are several ways to get them. You are guaranteed a 4 or 5-star promotion item from the following:
- Challenge and Mercenary Events
- Rare Spec-Ops
- Special in-game Offers
There are also several other methods which give you a chance to receive a 3 or 4 star promotion item:
- Wanted Mission rewards and high-level War Machine loot
- Alliance Wars loot
- Alliance War Chest loot
- Drive-In Cinema
- Raid Season and Raid Tier rewards
- Veteran campaign area completion rewards