Thoma, a fan-favorite character that arrived in Genshin Impact with the introduction of Inazuma but who only because available to play halfway through update 2.2, is an interesting prospect for people to build.
Thoma is a Pyro Polearm user. At 4 Stars, he should be pretty obtainable for most players from wishes without the need to hard grind Primogems and Fates that you can need to do to get your hands on the 5 Stars. Thoma can make for an excellent sub-DPS character for parties that are looking to add some Pyro damage to the mix.
The Engulfing Lightning Polearm is obtainable from Wishes and will increase attacks by 28% of Energy Recharge. This can result in a maximum increase of 80% ATK, and the weapon will also provide a 30% boost to Energy Recharge for 12 seconds after using an Elemental Burst attack. For lower-tier builds, The Catch is a solid option, increasing Elemental Burst DMG by 16% and Elemental Burst CRIT Rate by 6%.
For Artifacts, the Emblem of Severed Fate is a great option. The set is great for characters who have quick spamming Elemental Burst attacks, and who want to build large amounts of Energy Recharge, so is perfect for a sub-DPS like Thoma. At two pieces, it improves Energy Recharge by 20%, while at four pieces it will Increase Elemental Burst damage by 25% of your max Energy Recharge, topping out at a 75% increase of overall damage.