i've already read City of Bones and i know that city of ashes is next but i was wondering if i would be confused if i read city of glass before i read city of ashes, cause i recieved city of glass first and i don't know what i should do.

I think you should read "City of Ashes" first than "City of Glass". It is the second book and there are things in that book which are vital to "City of Glass". So if you read "City of Glass" first than you'd be confused as to how that happen or how you got there. It would feel like, you missed a whole chuck of the story. The books continue on with each other.

You have to read them in order! City of Ashes might not be my fav of the series but it's sooo important, I didn't get that until I'd read them about three times but it is really vital to the series that you read it first. So much happens, so much changes...Read them in order

Read them in order it will have the same effect if you read the last one instead of reading the 2nd book first trust me i have read the series 3 times and i still read them in order. Hope you like them!

Don't read them out of order because a lot happens in the second book that is referenced in the third, and it would get confusing. Plus, if you already know how the series ends, then CoA will be less intense and you won't get the full effect.

I think you'd get confused. There's a lot of vital information in CoA that's expanded upon and mentioned in CoG.