you'll find that riki gets less and less good the higher up you get in the skill brackets. lower skill brackets are full of players who have no idea what detection is and how to deal with riki (or bounty hunter, broodmother, clinkz, phantom lancer, nyx assassin, etc.)
riki's best skill is actually his smoke cloud thing. that thing is ridiculous. long duration aoe silence, slow, and sort of disarm. so good. i've even played a support riki before where i just snuck around and dropped that in teamfights in between stacking camps and warding/dewarding.
i don't think blink is a great choice on him. he already has a targeted blink, and you should be picking off people anyway rather than trying to teamfight. your job as riki is pretty much always to sneak around until the end of battles and get the stragglers or to quickly burst down split pushers or other heroes way out of position. you definitely should be picking up a diffusal blade because he quickly becomes insane when you grab one. you can also rebuy the recipe to get the charges back, iirc.