And what if it doesn't go down that much?

No, the question to be asked is, does the OP want to be a trader or an investor?  As a trader, he might make a small purchase now, see if it goes up or down and either buy or sell based on what his target profit is.  As an investor, he might make a larger purchase now and if it goes down he might buy even more, but the purpose would be to hold over the long term, not to make frequent buys and sells to attain small, short term gains.