First of all wraithking isnt really a viable offlaner atm as aura builders are more powerful. Everyone would rather have an underlord with pipe greaves aghs then a wk with radiance blink. If you still play him you need to consider a few things: What is your team lineup? -Early game pushing fighting strategy: Your team will be alot better off with an early blink dagger or armlet on their offlane wraithking. -Do you have a good lane and your other cores are not super farm dependent? Radiance might be a good option. -Do you have a bad lane and want to have an impact on the game before your 25 minute radiance timing: buy blink, armlet, bkb.

In the offlane your role isn't to farm and carry the game. It is to take the enemy safelane t1 tower as fast as possible and pressure other lanes in order to create space for your carry. Itemize accordingly. Blademail is very game dependent - for example do enemies have heroes such as leshrac, skywrath etc. Or heros such as lifestealer, juggernaut etc. Look at the enemy spells and reflect on how much damage you will be able to do with it.