I am thinking about runing 100 skinks in a 2500 point list is that too many or is that a good numbere I was thinking 40 with javalins 50 with blowpipes all in 10 man groups with 2 5 man chameleon skinks.
This depends on your army list as a whole and what you plan to do with it, so I would say there is no magic number. Skink-heavy forces have certainly been done before, especially in themed ones, but that many is pretty extreme, I must say. Provided there aren't so many that they just get clogged up, I suppose all those skirmishers (assuming at least some will be) could get pretty tough and annoying to deal with for your opponent, but once they start forcing panic tests on you an army composed of this many Skinks will quite likely begin to fall apart, and fast.
I've run lists that have double that number of skinks before and done ok. Just remember you need some sort of combat unit to play clean up and stop the the windscreen wipe cleaning up the entire army. Also for regular skinks, always go all javelins all the time, they are just much better.