+{s:bonus_bonus_damage} Desolate Damage : With current Desolate radius icreasing it's damage is pointless since it's unreliable.
-{s:value}s Spectral Dagger Cooldown : This kind of change will compensate Dagger's low linger time as well as boost your farming capabilities. The only problem is mana sustain, but Soul Ring and Scythe may help with that.
Starting Items
If the lane will be tough - get more tangoes.
Early
~7-10 min
Treads switch and raw tankiness may be halpful for Spectre in situations when you desperately need HP
~8 min
It's both farming and fighting item. With Soul Ring and Treads you're capable of clearing creep waves and stacks by using Spectral Dager and finishing off creeps with the Blade Mail passive
ALTERNATIVES: Hand of Midas, Meteor Hammer
Core
~18-24 min
Radiance is the best farming item you can get, but it slows you down quite a bit. It's better to get Soul Ring and Blade Mail most of the time (it will be enough for farming), but if you have a free early game and enough time to get Radiance then go for it.
Before Manta Style
ALTERNATIVES: Diffusal Blade
~25-32 min
Increases our farming speed by a lot, gives us a lot of damage against solo targets, increases tankiness by a little bit
Situational Early
ALTERNATIVE: Skull Basher
~13 min
Cheap damage and lockdown for more aggressive playstyle.
ALTERNATIVES: Radiance
Lategame
Gives a lot of stats and slow passive (which should work on illusions too), so it's one of the best items to pick up actually
Gives a lot of tankiness and good for locking people down. Most of the time you don't really need it or just have more important slot to have. Altho, it's actually pretty good as 6-7th slot.
A lot of attack speed, damage and miss chance. May be replaced by Bloodthorn if you have enough money.
Situational
Heart is that point of becoming out-of-control. It replaces any of your cheap regen items, while also making you very hard to kill in fights (not only because of HP pool, but also because of ability to get out, regen ad re-engage).
Good armor aura and attack speed buff. Good thing to pick up if you don't have it in your team and really need armor
Almost all the time you WILL need to pick up BKB. It helps a lot against disables, break and a lot of other stuff.
Other Significant Items
~10 min
ALTERNATIVES: Meteor Hammer, Blade Mail
Another awesome farming solution for early game. It's going to replace Blade Mail and Soul Ring, but it will provide you a lot of regen for early game
ALTERNATIVES: Blade Mail, Hand of Midas
It has a fairly low cooldown and works well as regen item replacement and a farming item. You don't really need to use it in fights, but you CAN if you need to focus a squishy target. It's better to purchase with some cheap armor (like Blade Mail)
Gives a lot of tankiness and sustain, BUT doesn't boost farming speed, while also being quite expensive.
Good for tower dives (and very agressive plays) or against summons/high attack speed.
Other Items
ALTERNATIVE: Orchid Malevolence