Não se trata apenas da parte final.
UPDATE CashShopData SET Gold=Gold + 3000 WHERE AccountID=@Account

CashShopData, contém as colunas: WcoinC, WcoinP e GoblinPoint.
Logo, ao rodar a query vai dar erro informando que não tem a coluna "GOLD". A não ser que esteja utilizando essa coluna já criada na tabela CashShopData para um webshop. Ai sim funciona, mas se for pra premiação interna você deverá escolher entre as três citadas: WcoinC, WcoinP e GoblinPoint.

USE [MuOnline]GO
/****** Object: StoredProcedure [dbo].[WZ_CustomArenaRanking] Script Date: 11/27/2015 22:13:41 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO


ALTER Procedure [dbo].[WZ_CustomArenaRanking]
@Account varchar(10),
@Name varchar(10),
@ArenaNumber int,
@UserScore int,
@UserRank int
AS
BEGIN


SET NOCOUNT ON
SET XACT_ABORT ON


IF(@ArenaNumber = 0)
BEGIN


IF(@UserRank = 1)
BEGIN


UPDATE CashShopData SET GoblinPoint=GoblinPoint + 3000 WHERE AccountID=@Account


END


END


SET NOCOUNT OFF
SET XACT_ABORT OFF


END


------------------------------------------------------------------------------------------------------------------
ou

USE [MuOnline]GO
/****** Object: StoredProcedure [dbo].[WZ_CustomArenaRanking] Script Date: 11/27/2015 22:13:41 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO


ALTER Procedure [dbo].[WZ_CustomArenaRanking]
@Account varchar(10),
@Name varchar(10),
@ArenaNumber int,
@UserScore int,
@UserRank int
AS
BEGIN


SET NOCOUNT ON
SET XACT_ABORT ON


IF(@ArenaNumber = 0)
BEGIN


IF(@UserRank = 1)
BEGIN


UPDATE CashShopData SET WCoinC=WCoinC + 3000 WHERE AccountID=@Account


END


END


SET NOCOUNT OFF
SET XACT_ABORT OFF


END


-------------------------------------------------------------------------------------------

ou

USE [MuOnline]GO
/****** Object: StoredProcedure [dbo].[WZ_CustomArenaRanking] Script Date: 11/27/2015 22:13:41 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO


ALTER Procedure [dbo].[WZ_CustomArenaRanking]
@Account varchar(10),
@Name varchar(10),
@ArenaNumber int,
@UserScore int,
@UserRank int
AS
BEGIN


SET NOCOUNT ON
SET XACT_ABORT ON


IF(@ArenaNumber = 0)
BEGIN


IF(@UserRank = 1)
BEGIN


UPDATE CashShopData SET WCoinP=WCoinP + 3000 WHERE AccountID=@Account


END


END


SET NOCOUNT OFF
SET XACT_ABORT OFF


END