For UB 1.1 (OP in my eyes): Played him just a few times (about 3-4)

Skillz:
First you need is Flash, but you dont need to max it.
Second should be Mana Combustion, that can be maxed when you are not fighting vs Int Heroes.
After that it all depends on the enemy. Ulti is good ofc so max it, it really needs mana combustion so think about it when you skill magebane.

Items:
Iron Shield
Steamboots (AGI)
Elderparasite
Runed Axe
Firebrand
Savage Mace

In that order. Iron Shield is my first item, its cheap and give good defence + damage up. Than i buy boots (not steamboots) and hungry spirit. You will be a bit faster and get hp back. After that i most times build Runed Axe and finish Steamboots and Elder after that. Sometimes i build firebrand next, because of the speed boost (it also boost damage and attackspeed). In the late game you can also upgrade it to frostburn, but you dont need to. Than last important item is Savage mace boost you damage.
After those items you can build something like Riftshards or doom bringer.

Playstyle:
He is an assasin, you cant run away and he sucks the mana that fast out, that the enemy cant use skillz. with your fast attackspeed and lifesteal + high damage you kill almost every hero very easy. There are just a few heroes who dont need mana and can really fuck you up. So try to kill nukes and int heroes. In teambattles you are very weak, because you got not that much defence.

Magebane need some hp, or not?^^
Upgrade firebrand to geomater bane before makin' luxurer SM^^

In retail you cannot life steal and mana steal at the same time... how does that work with magebane in HON LAN?

hm.. i didnt check it, but i think you can do it at the same time. and i dont need much hp as magebane, because my enemies die so fast and i can regen very fast with axe and elder.