In terms of minmaxery (that being the idea of "I want to get as many Tier 5 skills as possible as soon as possible, with as much power gain along the way the earliest it can be acquired") you'd go:
1 1 2 1 2 3 1 2 3 4 1 2 3 4 5 (then 1 2 3 4 5 thereafter, although I heard someone upthread saying that once you reached the last tier, other Tier 5 talents could be accessed outside of the pyramid constraint? Disabuse me of that if it's completely wrong.)
An alternative is going breadth-first:
1 1 1 1 1 2 2 2 2 3 3 3 4 4 5 (1 2 3 4 5 thereafter)
I imagine for most, the utility of certain choices will result in a hodge-podge of the two approaches.