C.O.
Each church is different. Call the church and ask them directly. Most prefer dresses to pants. but really? Unless it's an ULTRA-Orthodox church? They won't mind. Call them. Our church is Russian Orthodox. We PREFER women in dresses and skirts. shoes? wear what is comfortable. We are not some group of people that will look at your tags to make sure it's "the right brand" - I think you are wwwwwwaaaayyy over thinking this.
Gifts? it is typically the Godparents responsibility to provide the Bible to the child, as they are the ones expected to help in the religious aspect of the raising of the child. If you are NOT the Godparent, find out if they are getting the Icon for the child. This is a VERY touching gift. The Icon will be from the Month the baby is born. You can contact the church to purchase and have it blessed.
Another gift? The Baptismal candles...contact the parents or the church and ask if they have done that, if not - you would love to buy those. The candles are then lit every year on the anniversary of the child's baptism.
You also might note that several will bring bombonieres - Jordan Almonds in a small netted bag with a blue or pink ribbon tied. The Jordan Almonds go back to John the Baptist who baptized people in the Jordan River.
Savings bonds, etc. are typical. But really? People give all sorts of things at Baptisms.
What to expect:
The service will be long.
The Godparents will be asked to give "The Creed" - this is where the Godparents are asked to confess faith in Christ on behalf of the infant. They then recite the Nicene Creed.
you will hear a LOT of "Lord have Mercy" since you are Jewish, you are NOT expected to state this. It will be done after each Petition. there will be people crossing themselves during the service as well, since you are Jewish - you are NOT expected to follow suit.
When you hear "Peace be onto you" - you can respond with "and to your spirit"
Also be prepared...some Greek Orthodox churches DO NOT have pews. there are chairs for elderly or disabled, but mostly? people stand.
hope this helps.