i would say Ultra-Ball so you could save the master for Entei Suicune or Raikou
pokeballs are the best balls you can use just use one of them and then do the A/B trick(hold a and b at the same time) and it should catch!
Chat with our AI personalities
With a pokeball
Have a Fast Ball with you. This ball should catch at first time. If not, stack up on Ultras.
you use a pokeball
Throw a pokeball at it.
The pal park will give you special type of balls.