To upgrade a weapon fully, you will need to completely upgrade the Blacksmithinf feature by collecting all of the rune tablets for Gerlinda. You can find them in the Fitzroy Gorge Cave, the Mining District house before the Sunless Skien, and the Tower of Penance. From there, you will also need the following materials per upgrade level.

1. 2 Small Deralium Fragments
2. 4 Small Deralium Fragments
3. 1 Regular Deralium Nuggets
4. 2 Regular Deralium Nuggets
5. 4 Regular Deralium Nuggets
6. 2 Large Deralium Shards
7. 4 Large Deralium Shards
8. 6 Large Deralium Shards
9. 8 Large Deralium Shards
10. 1 Deralium Chunk

For a more detailed guide for crafting materials, you can read you crafting resource farm guide here.