You can always check this account on opgg etc for the build but I'll list it here as well.
5th item I usually go either
and I've even seen
, last item usually 
second or third is your choice, you get it to negate the ultimate range nerfs
Same thing, because of the ulti
is really, really strong right now, on every AD assassin, awesome stats, ms helps rengo, not to mention the passive.
This is the build I usually run, you can still try crit rengo, don't know which build is better,
's movement speed got nerfed, that's why most dropped it. You can go a different build if you feel this one doesn't suit you.
I wouldn't drop it at all, even if you need
, 1 out of 10 games you will need LDR and if you do need it, either drop
/
as your 5th item.
Win rate wise - in my honest opinion win rates mean very little, before the nerfs Rengar was played so much, he was either always banned or picked in every round where he was not, he didn't receive any buffs, he was popular because of the streamers like Nightblue3 (I love the guy, don't get me wrong), and because of the updated AD items. Rengar has always had a large player base because how cool the champion is, I main him for the very same reason, people just dump "freelo" champs after one nerf and never look back, champion mains stay and adapt after the plebs leave ;)
Edit: accidentally posted 2 identical comments, thus deleted one.