Dash is a versatile, low-risk class and a great tool for feeling
out the other player's shielding patterns.
As Dash, you should always begin a match by dashing toward the ball to arrive there before the other player. No other class, at the start of the game, can outspeed you (save Wind, but for Wind to reach the ball it must also push the ball away from itself and toward you on most maps). Gaining possession of the ball at any time is an advantage, but is even moreso at that start of a match. Considering that possession naturally flows in a binary fashion (from player 1 to player 2 to player 1 to player 2... etc), starting the game with possession of the ball should grant you one more chance than your opponent has at scoring points. Although most games of BOTOLO involve many exchanges of possession, any advantage is still an advantage. There's no reason not to take it when it is guaranteed.
Outside the tipoff, Dash's primary strategy should be to harry their
opponent into tilting. Quite simply, it is annoying to be hit by a dash,
since you lose control of your own movement momentarily, and it is even
more annoying to be hit by even more dashes. Players will often block on
your regular approach, and if your opponent is prone to do so, they will
often instinctively block when you dash at them. Your strategy here can
be to wear them down with repeated dashes. It is more mentally taxing to
be hit by a dash than it is to hit someone with a dash - doubly so if they
are blocking your approach every time and losing the ball exclusively by
wasting their shield.
It goes without saying that, as a Dash player, you should be looking for any opportunity you can to slam your opponent into a cutline. As soon as they get too close, one good hit can give you the ball for free. This nullifies the opponent’s ability to retreat from you on certain maps and can help you establish better control of the angling game. Note that even if no cutlines are present, it is still almost always possible to knock the other player off a zone they're capturing points in.
The further away from your opponent you initiate a dash, the further they'll fly. Dashing them from directly beside them will send them only a small distance, but dashing them from juuust inside the maximum dash range will send them much further.
As Dash, you should also learn to consistently execute the dash-steal.
Pressing A at the same time you activate your dash will cause you to
steal from the other player if your dash connects. This helps to correct
a weakness in Dash, in that typically much of Dash's gameplan involves
distancing itself from the defender. These frequent retreats segment the
time Dash spends within stealing range, which tips the block/steal game
toward the defender's favor. The dash-steal effectively increases the
range in which you may steal, somewhat compensating for time spent away
from the defender.
Remember that a dashed player can still move after being dashed, but will be unable to react to the fact that they've been dashed for a good 10-20 frames (based on average human reaction time). If you can predict and catch a player attempting to retreat from you, they will fly much farther than if they were approaching you. Dash, as a power, wins when it is attentive to the opponent's movement.