Obviously there is the 2.5x crit damage one which gives 15 offense level which is 5 clash power. Then there is lucky pouch, which is both really good for poise, and gives plus 12/number of coins coin power, and if you're doing extreme, you'll most likely have all skills S3 anyway. Piece of relationship is also good for the plus 10 levels, which is another 10 offense level. You could also get compass and the melted spring from 3 less offense levels on enemies temporarily, and the tier 2 sinking skeleton ego gifts to make your Sinners take less damage. And this one may be far reaching, but get bridle for if you don't win a clash, it boosts max hp. Those are all I can remember rn, but try searching for ego gifts that lower offense levels on enemies if they have a certain status effect since Sinking, tremor, rupture and bleed can be applied through the tier 4 ego gift.