I don't think you should judge someone without knowing exactly the circumstances. I was married for 3 years and realized it was a mistake and got a divorce. I met the love of my life just 3 years after the divorce and we got married right away. I wasn't too young, or irresponsible or rash the first time, and I wasn't any of those things the second time (being well into my 30s the second time). Sometimes things just don't turn out the way you want them so you do the best you can. And sometimes life just gives you a second chance at happiness.
My second wedding wasn't out of greed, and honestly I wouldn't have cared if we didn't get any gifts. I was just happy to share my day. The people who knew me and love me were very generous and wanted me to start my marriage off right.
Forget the fact that he's been married before. How well do you know him, and although it sounds kind of rude to put it this way, how well do you like him? If you like him a lot and want to wish him well, spend what you can afford and what you feel will give him a heartfelt gift. If you don't care for the person, spend what you feel is appropriate, or gracefully decline.
I dislike the old idea that a person who gets married a second time does not "deserve" nice gifts or a nice wedding. Every couple deserves a wonderful wedding and heartfelt gifts, no matter what the dollar amount spent is.