Riki 4 is ridiculously strong right now with the newly buffed shard. Let me explain:
Since IF nerfed all the cast range talents, supports are much more vunerable in team fight right now. Meanwhile riki has a shard that sleep the target for 4 sec, slow for 4 sec afterward with a 1000 CAST RANGE with 12 sec cd. If you have no good dispel or bkb, it's really painful to play against him since he also an AOE silence smoke. It's really hard try to jump him since he's invi and can initiate from really far away. His biggest weakness is of course the first 20 min when shard is not available. During this period, he's almost completely useless as a 4. If the enemy can gain considerable advantage during this period, the plan won't work.
For item, i usually start with boot into tranquil. rush a meme hammer and play split push until 20. Best thing you can do in this period is trying to take t1 tower with your hammer. If your team has stun setup you can also use hammer to help them. Your ideal lane partner should be a strong laner than is hard to die (LC, cen, dawnbreaker), run around and mess with their 5's pull is the best thing you can do.
After 20 min and shard, your best item is a dagger then a gem. If the game is even at that point, the enemy wouldnt dare to play alone since it's so easy to get caught. Use your dagger and gem to clear detection and vision around the map. At this point the enemy wont have vision to do anything risky. And you will starve the enemy's supports with detection.
Granted i've only played in ancient/divine bracket. But everytime it felt so effective as a support since you can always contribute without putting yourself into danger. The only problem is that it literally deal no damage, so your team need to make up for the lack of damage from your build