Just want to know among all of the town in Lineage,

1. Which is the most complete (all kind of shops/stores)?

2. What is the highest grade of weapon/armor/accesories that you can buy on the biggest town (armor, weapon shop)? Is C the highest?

1. There is not a "most complete shop". Every shop has its own purposes(selling armor/weapons, pots.. etc...)

2. As I know it's low B grade weapons from Giran Luxury shop. You can also buy shadow B grade weapons.

Shadow weapons are cheaper, but they disappear after 5 hours of having equiped them. So, u will have to buy a new one after it disappear or carry more than one on you. Also, they cannot be dropped/traded, add a LS on them or add a SA on them.

giran-->lux shop

Giran is the best option.
Ruud44 already told you what you can buy .I will add the low B grade armours sets from luxury shop .
All armours C grade -you can buy them from ordinary arm/wep shops.
From Jewelry Shop you can buy top C jewels.

Thanks for that info. So there is no option to buy like some B grade weapon (not the shadow coupon)?

Well the only option I can see is to buy it from people selling stuff I guess... getting then via raid boss drop is definitely hard especially when you know few people who would like to go boss hunting.

1st there are no B grade weapon exchange coupons, you have to pay about 90 k for b grade shadow weapons.

2nd As I said you can buy low B grade weapons from the Giran Luxury Shop in T2.

wehee all mages can now have valhalla+acumen

and gladis, bd can have kesha*kesha easily