Check on what's happening mate. If the dip has been for weeks, and you foresee it to continue, maybe you should wait a while because it may go down some more, and so, if that will be the case, then you can use less capital to buy more coins. However, if it starting to see some gains in the past several days or weeks, then it would be much better if you would buy now before it actually regains value and that would make you shed out more money to buy for less.