Sion is my most played jungler this season so far (like 80% of my jungle games have been him and I main jungle), and he is really pretty great. The best way to play him is start W and if you are starting blue buff side, Smite Gromp and clear that whole side, back for your upgraded jungle item if you have the gold, or try and clear one more camp (Scuttle crab is great for this) and then back before clearing red side with your upgraded smite. On red buff side, start at Red, get a leash and smite kill it so you don't use a pot. After that, kill wolves and then Blue buff (and Scuttle crab on that side if it is up). If you are healthy after that, gank top or mid, if you aren't back for your jungle item and clear the rest of the camps (Gromp, Raptors, and Krugs) and then look for ganks. If there aren't any lanes shoved in towards your team, look to farm till 6 and control vision like warding and Scuttler, and watch for countergank opportunities. Once you hit 6, you just do lane ganks. Even if you miss your ult, you can usually get them to burn flash by charging past them if you can't get a direct hit, and even at max your ult is a much lower CD than flash, so it is worth if you gank before their flash comes back. For items, go
until 6, and then swap it for
once you can afford the enchantment. Get
next (go Phage>Sheen>Zeal) and then pure tank. Warmog's is great for junglers right now for sustain in between ganks. Other than that, think about Locket, Randuin's/Frozen heart, and building boots of choice (you get tenacity from Juggernaut, so my personal Favorite is either
or
, with either Furor or Homeguards).
Hope you like how he plays (By the way, if you could make
work for you, then Sion should feel amazing!).
EDIT: Here are some other suggestions to try out:
and
(he actually works pretty well because of armor stacking and his AOE for clear, stun for ganks, and heal for sustain).