Always buy more, if you are not sure now split it up to more timepoints in the future. Could be daily or twice a day.
maybe you buy them at a better price when the exchange rate falls and when it rise your previously bought btc will make it some what up.
This is what I was thinking of doing... buy a little bit by bit and catch the upside as well as even out on the downside, but get the benefit of the upward trend