1)I think that first you need to determine a definitive number that you would not want to go over. Then take the time frame you plan to marry and divide it into a monthly savings goal. Look for high interest savings accounts that will make your money grow.
2) You should also determine what is most important to you , your must have list and cost out what you want to pay for each.
3) Identify what things on that list you can do yourself, or maybe a talent that one of your guest can provide you as a "gift" i.e photography, videography etc.
4) continue to re-evaluate your list and you might find out that your previously must have list may become smaller and therefore decreases what you have to save.
Remember that this special day is really about you and your FI and what people usually have at weddings may not be what you really want to have. Traditions only matters if it really matters to you.