Best way to power LED strip (180 LEDs)
There are a few useful guides on the Adafruit website about powering these strips, including this one showing the addition of power taps.



The flexible pcb won't handle the current of a long chain fed from a single end without excessive drop in voltage to the far end (if not burning out the traces at the start end competely) and causes color changes along the chain, so you need to connect taps in every meter or so with heavier wires in parallel so that each LED is no more than half a meter away from a tap held close to the nominal supply voltage. 

If the current draw is too much for a single supply, you can break the 5V supply every so far, and power each section from a different supply . In any case, the only current flowing to the Arduino is its own supply current.