The item build will make riki more faster and more kill in early game. Therefore, try to reach lvl 6 ASAP for invisibility it will make killing easy. Always attack from behind, cause backstab give u more damage and the sound is more cooler.
How to Approach The Enemy
It depend on your skill make sure u have all the skill.
IF YOUR BLINK COOLDOWN IS LONG
approach behind the enemy put smoke screen, as soon as u put the smoke screen attack and kill the enemy. use blink to get behind the enemy for more damage or use it when the enemy try to escape.
IF YOUR BLINK HAS FAST COOLDOWN
blink to the enemy and smoke screen, keep attack the enemy to kill. use blink to get behind the enemy for more damage or use it when the enemy try to escape.
always beware of the enemy item whether they have gem/dust/ward.
stay away from slardar/bounty hunter, let them use their track skill first then only approach.