I typically get movement speed on Trist when I play her:
Of course, mid game I get out dps'ed, but this build makes it possible to harass enemies more effectively early to mid game. Then, late game, when I need the dps, I go dps. Also, if there is a mega-tank on the other team, then you may want to go for Madrid's Bloodrazors... In addition, if there are a lot of dps heros on the other team, the consider going for the frozen mallet sometime mid game.