For skill order Max W if you're mid, I'd still do it to poke out meelee mid laners and shove waves so I can roam, which is his entire purpose anyway. For top lane, you max Q so you can trade more with your passive.
Thunderlords is good, but I think stormraiders is best on him as it is useful throughout the entire game. A stormraiders speed boost can mean the difference between assassinating a target lategame and getting out alive, or dying and making your team lose the fight. Also, stormraiders just helps you stick on your target better to get off that last auto for your passive in situations where the target flashes or dashes away. I also prefer precision over 45% CDR because the extra lethality will just be more consistent than .4s off your W or Q. Ult already has a relatively low CD.
As for build path, I go Ghostblade first because the active is just too good for engaging and disengaging. Combine that with stormraiders + cleaver MS + swifties + E and you will be an uncatchable god. I like go to second item Duskblade usually, but if I'm a little behind I'll grab a 2nd item cleaver to help me survive and have the CDR to farm.
As a 4th item I like to get Death's Dance because it caps my CDR, helps me survive, and the heal from a crit Q is insane.
5th Item is very situational and depends on the match. If you're ahead enough you can get IE, or even earlier. Other options include Steraks, Maw, Edge, GA etc. Of course if you're up against an AP mid, or lots of AP in general, you'd want to fit in an early hexdrinker/maw
The reason why I don't build hydra anymore is because his new W clears waves pretty well on its own. You won't be really using the hydra active in your combos as much as old talon because of how Q is now a double AA reset. So there isn't much room to fit in hydra before either you die, or your target dies. IE is also very risky when it goes to late game because you essentially become a walking balloon. ADCs will be killing you in ~3 or 4 autos.