Pushing Lanes and Ganking like a boss!

I'd suggest you to add a Orchid Malevolence to your build, it's a really good item for Furion, it gives him really easy kills :)

Also, get Teleportation at level 2, not Sprout, it comes in handy, you can catch fleeing first bloods or even couriers if you are careful.

When ganking lanes you want to max out teleportation first to have global presence every 20 second.
1 point of sprout is enough early game, and you max treants second so you can random push lanes when you have maxed tele. Ultimate is taken everytime you can.

About the items, I would suggest only get RoB when jungling with treants, but apart of that midas is a good item for furion, extra extra farm for him. Furion can gank at lvl 2 with 1 point of tele and sprout, and when he rushes Midas, you should be having gloves of atack speed for more DPS during the gank.

Overall, good begining, try expanding this pls. +1