Trade guild enhancements allow a guild member to spend less money on any service provided by npcs (be it items you buy (-5/10% less) / sell (+5/10% more) or item upgrading / sealing, NOTE: this also influences the prices services provided by maidens ).
As for treasure hunt - it's just +some percent to the basic chance of item drop (no distinction here). It works same as say the premium shop clover (though with much lower +% chance). But if you want exact figures for drops - no one will be able to tell you as the developers explicitly refused to provide any information on the ingame mechanics justifying it by the pleasure of exploring and finding everything by the players themselves.
1 important thing to mention here: a guild member will enjoy the guild bonuses ONLY after he/she contributes 100k+ experience to the guild (you can always check how much a separate character has contributed by calling the guild members dialog and hovering the cursor over the desired character name).