My belief is that attack rating is the speed in which your character attacks with his or her weapon. I've not been able to confirm this however.
As for trade goods, I havn't seen such a guide myself, but it wouldn't suprise me if one existed somewhere.
Good luck with it. I can give you a small piece of information for 1 star trades:
(this is with the 1mil Trader suit, 'Red Flag')
Lv37 with Bactrian Camel at lv2 Trader holds 94 Blue Celadon/Saddles/Crystals and 1 Red Silk/Leather/Agate.
Lv38 with Bactrian Camel at lv2 Trader holds 96 Blue Celadon/Saddles/Crystals and 1 Red Silk/Leather/Agate.
Lv39 with Bactrian Camel at lv3 Trader holds 98 Blue Celadon/Saddles/Crystals and 1 Red Silk/Leather/Agate.
I think there is a pattern.

And Trader level doesn't seem to matter, contrary to my former belief.