Boots on trynd are a waste of hard earned gold. The only ones that would be worth getting post patch would be the cooldown reduction for his ult, but as much as it pisses off casters you can just grab up a blue buff and there you go CD. Phantom Dancers should be a main recommended item for him idk why they aren't. You get movement speed, attack speed, and more crit chance than any other item in the game. Phantom Dancers are why you don't need boots. You are as fast as everyone else who has boots with only having one PD plus it increases your attack speed by more.

The Infinity Edge is a no brainer, you want to crit with Trynd you want to do lots of damage with trynd this gives you both. BloodThirster is the next key item for staying and banging longer without popping your ULT and being able to bang when you don't have one. These are the three core items. For me the match is usually over when I get these three. From here it depends on how the match is going for you. If you need to crit more and you think you are to slow grab another PD massive crit attack speed and more movement speed. If the enemy is stacking armor because you are merc-ing them with bombs crab up the new Black Cleaver attack speed and damage plus the nice armor pen.