Whatever amount you can afford to give.
nothing
Any monetary gift is based upon what you think is right and what your budget can afford.
Gifts are not customary at an engagement party because they are expected at the wedding and etiquette dictates that those who are invited to an engagement party should be invited to the wedding. If you choose to give a gift you can but it is not required or expected.
What a selfish and foolish question. They already received it most likely!
Be sure first that the bride and groom have not got wedding registries at different stores and if they have you can go to any of those stores and buy a gift and forget giving money. If the bride and groom to be have requested a monetary wedding gift then anything from $50 up is just fine. Don't break the bank over it.
It is just fine to give money instead of a gift at a wedding in England. Some couples prefer the money to buy what they want rather than getting duplicate gifts or gifts that do not suit their lifestyle.
Is it customary to bring a gift when you are invited to a barbecue?
It is customary to give the ushers a small gift. Maybe you can give them a craft or something interesting, you can search it online, This site you may have a look~
I don't think you should if you weren't invited to the wedding. In polite society, gifts are NOT to be expected. If you want to send a gift it is up to you whether you get an invitation or not.
No one should give more than they can afford for a wedding gift. The general monetary gift could be anywhere from $50 and up. If you are uncomfortable with giving money then buy them a gift.
Regardless of religion or social standing the most common gift at Indian weddings is money whether the amount be in pounds or dollars, jewelry is another staple of an Indian wedding because of its strong presence during the wedding itself.
You should only give a gift if you feel you want to. However, a card is always appreciated.