1. Stellar Amulet
   This is the prime target for chancing due to the possibility of obtaining the highly prized unique Astramentis. This item is extremely rare and valuable, making it a high-risk but potentially mega-reward gamble. The Stellar Amulet's base item itself also holds value, so using an Orb of Chance here is a significant choice for anyone managing their poe 2 currency carefully.

2. Heavy Belt
   The Heavy Belt base type is sought after primarily because it can be turned into the legendary unique Headhunter, one of the most famous chase uniques in the game. Although the chance is low, the pay-off is very high. A secondary unique from this base is Waistgate, which is less valuable but common, balancing the risk somewhat.

3. Sapphire Ring
   Chancing a Sapphire Ring can yield the unique Dream Fragments, which hold insane value. Compared to other top-tier uniques, these are slightly more common, giving this base an attractive risk/reward profile for players willing to invest multiple orbs.

4. Emerald Ring
   This base item offers two valuable unique outcomes: Thief's Torment and Death Rush. Both have high utility and good market value, and the chance of success is better than the ultra-rare uniques on some other bases. This makes Emerald Rings a smart mid-tier target for chancing.

5. Gold Ring
   Chancing Gold Rings can yield Ventor's Gamble and Andvarius, which have variable value due to the wide range of modifiers possible on Ventor's Gamble, and a more consistent moderate value on Andvarius. This makes Gold Rings a fun and potentially profitable gamble, with some risk reduction from the consolation prize unique. Players who keep an eye out for buy poe 2 currency deals can often fund more attempts at these lucrative bases.

These items mostly fall into jewelry types (amulets, belts, rings) because many high-value uniques accessible by Orb of Chance are currently limited to these in PoE 2's Early Access. While there are powerful weapons and armor uniques, many of those are not currently chanceable due to base type restrictions.

Aiming for Stellar Amulets, Heavy Belts, Sapphire Rings, Emerald Rings, and Gold Rings offers the best mix of high-value unique rewards and achievable odds with the Orb of Chance. These bases provide a balance between potential reward and relative feasibility, making them the top choices for players looking to master chancing in Path of Exile 2.
Always remember that using the Orb of Chance involves significant risk, and even these targets will often result in magic or rare items rather than the desired unique. Approach with a clear strategy and the willingness to accept losses for the chance at legendary rewards.