No matter how much I want to be a fortune teller, I can't say how much the coin will be worth in the future.
You can buy Golem on Bittrex, Poloniex, Cryptopia and many other exchanges.

In the future you can always see which exchanges trade the coin you're interested in by going to coinmarketcap.com and search the coin you want, then under the "markets" tab you'll find all the exchanges that trade that coin.