>>278487571st move: bite/dragon breath, both around the same level of good depending on situation, though low power on the defensive
2nd move: 5 charge twister isnt as good as 2 charge dragon pulse or hydro pump, which is probably the best as a STAB one charge and the only water move it gets. honestly twister is supposedly the worst but in a defending gym it isnt terrible, since it charges up and goes off very often, and people just dont know how to dodge it. that being said, hydro pump>dragon pulse>twister.
i would wait until ~level 25-30 to find a higher cp higher iv gyarados. having caught almost 2000 magikarp ive evolved maybe 20 of them and only got twister 3 times. ive also seen 5 in the wild using a tracker, but only got 2 of those
