The Agility Abuse Guide

diffusal is a much better choice than sny. It gives u a reliable slow that ensures a kill in a gank, and gives you 22 agility, which means a total of +50 dammage when backstabbing, and great 22 attackspeed whick will wreck anyone purged under smoke, not to mention +3 armor from the agi which helps a little vs physical dps. and diffusal is cheaper too :P

-1 because of sange and yasha

sange and yasha is TERRIBLE. Don't ever buy it, seriously Manta Style is so much better for Rikimaru.

Very good guide, well done!
Correct me if I am wrong, but i still don't think Ethereal blade is a better option for riki. Ethereal is 1100 gold short of butterfly and gives just 40 agility plus very nice 10 int 10 str stats. However, butterfly gives 30 agi and 30 dmg and attack speed. For agi hero that 30 agi will go to another 30 dmg and attack speed. in total of +60 dmg, attack speed and 30 agi to ur backstab. Not sure if that 10 extra agi will make backstab more effective than what batterfly adds in damage. Besides that 35% combined with smoke miss chance will make riki great initiator right? Blink, smoke it up and while enemy team focus you, your team focus them all. Haven't tried this yet, but seems doable.
Anyway, I do see Ethereal blade as excellent choice especially if you get counter picked as it is more defensive with it's active.

I'm new to dota, still figuring out how stat stacking. So, if I'm wrong let me know.

I enjoy the items, but the leveling os really weird. Because, your Q is just awesome, you should level it at level 3 and max it at last.
And not at lvl 10...

but nice anyway +1

My maths fail me again.

I think I was taking into account the other stats. Still though, you're right.

Ironwood: 53g for 1 agi
Slippers: 150g for 3 agi

53/1 = 53
150/3 = 50

50 < 53

Therefore, slippers are more efficient than ironwoods. QED.

Actually, Ham, you are wrong. The correct answer is Iron Branch.

Most cost-efficient form of agi is slippers. O SNAP.

Interesting guide, I will try this soon, although I don't completely agree with your opinion about SkullBasher.. + 1