Pretty straight forward, relies on heavy spin damage, clearing waves of minions early and late game. More crits = more spins, so you can take out the deathfire and substitute another PD if you want more spins rather than a stronger one. With ap, Spinda's Q heals him a bunch, especially with max fury, even when it is level 2 or 3.
Note, this is my first guide, so I'm sorta winging it as i go >.>

Pros

+Clears waves very Fast
+Insane sustain
+With his ult, Even better (may not even have to use often)
+In teamfights, with proper timing, spins can hurt a LOT

-Doesn't hit as hard as other trynd's
-1v1 capability isn't that high

You can really get whatever you want, other than clarity or revive because they are COMPLETELY useless on trynda, but I grab flash because its like an extra spin, and is especially nice for juking those shaco's and tristana's and the such with over/through the wall movement. I also get surge because it will boost the effectiveness of your spins, and depending on your crit, also increase the amount, making it very handy in teamfights.

They are what they are- CD boots for spins, Deathfire to whittle people down before slicing them in half, guinsoos+PD to increase spin quantity and damage while laning, Rabs for sheer power, and Hextech gunblade for the spell vamp and life steal.

ap per level is usually what you would grab on a lot of manaless ap's, I mean really.

There is no set order, just be sure to have at least 1 point in mocking shout and 2 on your Q and spin at level 5. Depending on what you need (Dmg vs HP), the rest is up to you. Grabbing your ult whenever you can is a necessity, I mean, Its TRYNDAMERE (Strong like Panda bear)

SPIN SPIN SPIN NO MATTER WHAT. Q Q Q when you need the HP. Ult when you're about to die. Nuff said.

Never. This is what you would do with 3 or 4 other guys in a team, and you ll feel like trolling. Ap Trynda is HIGHLY unreccomended in ranked games, as it is very risky.