Not Updated For Current Season
This build is not the greatest early game build but that is ok. The way that I like to play my Trynd is I like to get him up to his killing potential as fast as possible. Be warned that early game will be very difficult, but once you hit about level 10 you should be able to murder most any champion.
Start with the Brawler Gloves because they give you a bonus 8% crit chance, which allows you to not only deal a lot more damage while jungling early, but also allows you to heal (by using bloodlust). Get the avarice blade simply for the money, since you buy it early it will definitely repay its cost in the end. Follow that up with Berserker's Greaves for the additional attack speed since more attacks means more crits means more win. While you may think that it is over kill to have two Phantom Dancers, I say differently. The fact that they give you move and attack speed on top of the crit chance makes them my favorite item to use with a dps champ. Obviously get the Infinity's Edge for the bonus crit chance and bonus crit damage. I like to get it in between my two Phantom Dancers because it allows you to put out a lot of damage and start ganking (if you haven't already). The final two items (Stark's and Bloodthirster) are totally optional. If you don't want them get something else. However, do not get anymore crit chance because you already have over 100%. I like to have Stark's because it boosts you and your allies, AND it reduces the armor of the squishy food that you are swinging at. I also like to end with the Bloodthirster because it not only gives you a lot of lifesteal, but it gives you a lot of damage as well, especially because you should not be dying late game.
Start off by chilling in the bushes next to the wraiths. Smite the large blue one and begin swinging at the others. They should drop (with you healing whenever you get 8 bloodlusts or after a battle) leaving you with about 3/4 or more of your health. After that travel to the golems, using a health pot on the way. Attack the golems which you should be able to kill (it might get very close, use another pot if necessary) then go back. You should have just about enough money for the avarice blade. Travel to the wolves and finish them off (remember to smite the larger one). Repeat until satisfied. You should be able to get the blue buff at about level 6 or 7 (maybe sooner if you are feeling risky).
Many people dislike how I play mid game, but I find it works really well. Unlike most I like to stay in the jungle and jump out here and there to get a kill or two. Once you get your first phantom dancer you should have a pretty steady flow of crits rolling in and a nice health recovery from bloodlust. At that point I would suggest grabbing a couple of ganks. If you are not comfortable with ganking then, wait until you get the infinity edge and all will die before you.
If you can make it to late game, congrats, you won the game. This build puts out close to a thousand damage a second with an invulnerability option just in case you wanna get a 5v1 kill and still get out. Also with the life steal thrown in there you can easily take on 2 or 3 people simultaneously. Kill the first, attack the second, use undying when needed and heal on the third.