The bride said just a simple white wedding cake with beads around and real flowers on top for 100 persons. And how much? I am planning to make 3 tier cakes, what sizes? Please help me, this will be my first wedding cake. Thank you all.

I know there is a chart here on cc you take a look at it servings & sizes and all that good info. As for price most people charge per serving, but I don't know how much cakes are in your area. But the chart here on cc is pretty basic.

14, 10, 6 gives you about 116 servings based on a serving size of 1x2x4, not including the top 6" tier.
12, 9. 6 a bit less (I think 8.
Pricing depends a lot on your location; what cake flavor (special or 'normal'); what icing and your skill level. I recommend you charge at least $2 per serving. And you charge for all the servings the cake makes - not what they asked for. In this case it would be 116 or 88 times whatever price you decide to charge.

Maybe this can help,even though it's in spanish
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1212777

http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=88648

Found this again,maybe it'll help

Thank you guys for all the infos. The flavors are banana and yellow cakes. Fondant icing.