From our wedding experience, I definitely agree with one of the earlier posters that suggested getting people to donate to your fav. charity instead of giving you presents!
At our wedding 2 years ago, we told anyone who asked about what to get us either that there was no need to get us presents or if they insisted on getting us something, then we would prefer cash as we were renting an absolutely tiny house at the time and had no room for presents. Generally speaking, guests (especially the older ones) were not comfortable giving cash so we ended up with a lot of stuff that we had to get rid of because we didn't have the room for it. The most popular gift was paintings, followed by mantel clocks! The paintings were particularly frustrating because they were given to us unframed and we didn't have the money, wall space or appreciation of the compositions to justify forking out the money to get them framed - so they remain rolled up in the attic to this day, which is such a waste!
We also got a lot of vouchers, which I thought were great at the time but have turned out to be quite a hassle as they all had 12-month expiration dates and we weren't in a position to buy anything in our first year of marriage due to space issues, so all the vouchers have required a lot of fighting with companies to get them renewed. I would never give a voucher as a wedding present now that I've been through that.
Regarding the few cash gifts we did get, we ended up with about 4,000 euro - half of which came from 2 very generous family members. We had 90 guests in total so from my experience, if you are counting on your wedding guests to offset your wedding costs, it's a huge gamble that isn't likely to pay off. My advice: limit your guests to the people you REALLY care to see you get married and they'll feel very special for getting an invitation, and forget about the gifts altogether unless you want to try generate some awareness for a fav. charity among your guests.