Theres some more ways where you can get small amounts of upgrade materials.
1. Trader ships that are in front of the islands
2. Guild bloodstone trader in big towns
3. One more trader where you can trade the shards you get in chaos dungeons for some materials
4. Events like ghostship/Chaos portal
5. Completing dungeons on the main continents on easy/hard difficulty
6. Market place (especially t1 materials are pretty cheap to get for gold now)
But yeah, islands give most of the materials.
Most of the traders have a weekly limit that you can trade.
Hope this helps your progress a bit
This post was edited by Winternights on Mar 1 2022 07:28pm