Phase + Aquila > Drums and roam/team fight early. You can help your team an amazing amount with rank 4 dagger and blink strike and 1 in evasion - PA is actually very hard to kill this early (huge base armor + evasion + mobility). You should already be able to pick up kills at this point, easily, especially on weak supports, but even on lowly farmed carrys (AM is a free kill with a well timed dagger (it gives vision of him and after he blinks away you can blink up to him to chase)). Go for BKB next if you need it, otherwise I like basher and yasha unless my income is very high and I can finish manta (or SY - this is one of those heroes it's actually good on)/abyssal in a timely manner.
All in all, PA is not weak at all early game. Her dagger spam has an EXTREME amount of utility behind it.
http://dotabuff.com/matches/250263009
Too bad the replay is expired and, of course, I wasn't streaming for some reason it looks like so I don't have it recorded, but this game was a great showcase of PA's real power as a hero. There were a few team fights early (level ~9s) where I sat behind trees at 100 health and simply spammed dagger at people for kills, the slow is very high for such an extremely long range and the damage honestly isn't bad, either.
You can see that AM tried to rush battlefury but their team already lost the game by the time he got it.
tl;dr
Build PA like a hybrid carry and help in team fights early on, get your gold from heads not creeps. I really don't like PA for AFK farming, her base damage and attack speed are way too low to beat a hero like AM. If I had tried to go Bfury and beat AM in this game we probably would have lost.