What niche site to run for bulk without illegal content to CPM?

hi! need to create site, almost for bulk traffic etc running in CPM purposes, so need an idea what niche it should be - to look good with 50k/day traffic (little blog will look strange with such amount - that's main issue),

so what type of site to create as web archive copy will be best - to run and forget it for 3-6 month before next?