Poles are easy. The more money you spend the better they are. The higher the price tag the stiffer and lighter the poles are. The stiffer and lighter the poles are the less energy is required from you to move yourself forward. Simple. Buy the most expensive pole you can comfortably afford. You will be very glad you did.
General fit guidelines for race poles are:
Skate poles should come up to the mouth or slightly higher when standing in normal street shoes.
Classic poles should come to the top of the shoulder or slightly higher when standing in normal street shoes.
Always err on the long side. Poles can always be cut. They cannot, however, be lengthened.