My understanding is that it shouldn't matter! That's the point, you don't need to make any decisions really, or look at any charts .... other than deciding how much you want to invest over what time period ;). The sooner you start, the sooner you build the position.

If the price falls from here, then your later purchases are going to be better value.
If the price rises from here, then your early purchases are going to turn out to have been good value ones.

Disclaimer: this is not trading advice :)