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[Sebatianos]

Not everything you get is useful!
Also remember this - if they tell you you have nothing to trade - that means they won't trade with you (may be because they have nothing to trade).
I remember the first time I finished the game - I was so frustrated at this point, that I started randomly flying around and came to a place in space with a strange Korok ship - it was MR1's ship and I destroyed him. End of story (I never found out about the Less Ten though...).
There are multiple endings, but the game get harder and harder by the end, so you wouldn't simple repeat - the attack, trade, find out stuff, go on errands and attack some more - routine.

Good luck!