Whatever amount you can afford to give.
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.
You should only give a gift if you feel you want to. However, a card is always appreciated.
You can give your fiance his wedding gift the day before the wedding or on your wedding night as it should be private when the two of you exchange gifts.
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.
If you have not been invited to the wedding then you should not send a gift.
Yes, if there is a wedding in a church and a reception then you should give a gift even if it is a third marriage.
If you were invited to the wedding and can't make it because of traveling plans then yes, when you get back you should send the couple a wedding gift.
Judge & Mrs.
The best gift for your neighbor is something he or she can use. If your neighbor loves coffee, get him or her a cute coffee mug. If your neighbor enjoys gardening, a good gift would be annual flowers or bulbs.
The bridesmaid can give the bride a gift on the wedding day. However, sometimes brides will have a bridal shower, and if so, then that is when the present can be given.
Your gift should be at least the cost of your dinner. So if your dinner is $25 per plate, your gift should be at least $25 per person.