If I place a purchase order in the amount of 100 BTC, can I manipulate the price? How many BTC do I need to have to make the price shoot? The term "whale" is assigned to the people who own how much of BTC?
Over 2000BTC will grant you "whale" label. I have observed enough pumps on Mintpal, Cryptsy, Bittrex and Poloniex for nearly 5 years. 100BTC is a good investment in ICO, but nothing more. 500BTC is your magic number if you want to move a price of a new and promising coin with good volume like ICN. Keep in mind that move, doesn`t mean pump. With 500BTC you can move price on Kraken. If ICN is on Poloniex, you will need bots which costs 300-700 euro and at least 3000BTC. Keep in mind that top 10 coins are always into the spotlights and many people doesn`t place sell orders, but are keeping their coins on the exchanges and waiting for good price. You will also need 5-15 real people to create enough hype in forums, Facebook, Twitter, etc. You can not do it alone. So, are you ready to become whale?
Whale is a relative/subjective term. If you had 3000 BTC and asked Warren Buffet if he considers you a whale he would laugh like this:
Yes. I was talking in terms of pumping ICN. When ETC was about to be PnD for the first time, you remember that volume just on POLO was more than 120K BTC. And how about pumping BTC.
I am sure that even this old man from Omaha or at least his right hand - Charlie Munger will think twice about calling himself whale. 
Actually tbh 1000 BTC is a whale, he has 1 million usd in crypto, who knows how much he has elsewhere? With 1000 btc, you can pump any coin, 1 million usd can slightly pump even bitcoin for 10-20 usd. And can pump huge on ethereum if you have 1000 btc to be all-in eth.