actually i've been playing razor for quite some time and u should go for radiance first. heres my build:

lvl1: go for 2 ring of regeneration and skill is chain lightning
lvl2: the aura
lvl3: aura
lvl4: chain lightning
lvl5: aura
lvl6: storm seeker

the key area here is to max out the aura as fast as possible coz together with the 2 rings u can hold up to the nukers in early game plus u dun need a boot of speed yet. by lvl 6, or 5 if you're good at farming (smart use of chain lightning) u should have $3900 to buy sacred relic. the point of NOT maxing chain lightning before aura is becoz u'r not an int hero and maxin lightning will increase its mana cost. remember: u want to chain AS MUCH AS possible, NOT chain AS HARD AS possible in early game as your mana is limited. after getting radiance, go for a boots of speed to upgrade to boots of travel and PERSEVERENCE. remember: get the boots, void stone, ring of health, then only boots of travel. u want the boots of travel so u can teleport at points wen the enemy with their HORDES of creeps at comin for your towers. stand beside your tower and see the money fly. plus: the boots will make u move like superman!! WHEE!!

the point of doin this is bcoz so u can get a good flow of money before goin to a deso/buri build or Maskofmadness build or and 2ND radiance build.

just wanna add sumting 2 that:

wit d implementation of patch 1.18, if swen bolt's bonebone while bonebone activates windwalk, the bolt wont work

urza is normally played (where i play, that is) as early and mid game hero. His main specialty is to ensure there WONT be a late game, as he goes around killing heroes while team mates bust into the defence. (team play is important)

the way i play him? get a bkb, aim for soul booster, power threads. go out, chase them enemies down wit empower, slash em up, earthshock, slash slash slash... works most of the time. he is weak against gangbang though. but 1 on 1, as long as u have bkb its no prob. (earthshock plays a role here)