There is no dragon amulet. Off the top of my head, potentially the best amulets consistently in the game are in one of the 4 rooms under the tiles at the bottom of the Aleroth catacombs, in castle Stormfist in one of the houses, and from the holy item quest (if that is the choice you make).Gathering the Holy Items and the Sacrifice
The dragon breastplate can be upgraded. The dwarven king and smith will tell you about that after you have done some stuff for them (stone axe quest).Dragon Armour Quests
For the other dragon armour, you can reload a few times to try to get decent stats, but don't waste too much time on that; it really isn't necessary to get the best possible equipment.
If you quick save before running your mouse over an item/chest/merchant or hitting the alt key, you can identify the item or trade with the merchant, then quick load to get different stats or inventory. This can be done repeatedly to get the best stats or specific bonuses on an item (save after finding good candidates) or looking for specific items (such as spell books or charms) from merchants.