The easiest way is to use FHG's (Free Hosted Galleries). Get yourself a gallery script like AutoGallery Pro, ArrowTrader, or Comus. These will all have bulk import options. After you have the site setup, signup for sponsors that have FHG's. In the Sponsor's Affiliate area, you will be able to export a text file in a format compatible with your gallery script. Then just import the Sponsor's file.
Creating your own galleries from zipped content is better, but it will take more work.
Be sure to stick with the theme of your site... if it's a teenie theme, then don't throw in Granny galleries.
We have FHG's along with numerous free marketing tools for you to use at
SammySmack. Check us out!