I love Spectre! I've been carrying a lot in our little 5 stack and Spec is one of my favourites. I used to ALWAYS max dagger first and didn't really think of trying anything else, but recently have taken to maxing desolate instead, with one in each of the other skills. It lets you do a lot of damage early on if you can get it to activate while smacking someone, and makes you somewhat dangerous while still having a value point in disperse and a dagger point for escaping.
Desolate doesn't seem like much at first glance but being true damage makes the values a little misleading. Dagger only gives you a little more speed difference and a bit more damage for each point, which doesn't do a ton for a skill you will be using to escape over terrain with and can only cast a handful times due to the mana cost. With 4 in desolate at level 7 your illusions can hit pretty damn hard right out of the gate if your enemies are positioned incorrectly.
I might try Vanguard again sometime, but I find that it just slows down your other items, even just the RoH is such a bummer to have to get some games (but sometimes you need it). Especially if you max dagger, you are just useless for a big chunk of the game when it doesn't have to be that way. Radiance is different beast and it's best if you can get it fast, which I think is the advice that goes for lots of heroes that want that item. I think before vanguard if you can swing it, but obviously if you are being pressured that can be tough. I tend to view radiance as a farming item so the earlier the better if you are going to get it.
I usually go phase, Orb of Venom, then go right for diffusal or sometimes directly yasha --> Manta. Manta is kind of expensive to get right away but it's just ridiculous with desolate if you can activate it on someone successfully. Lately I've been getting Skadi after that which is amazing for chasing and helps a lot with HP/Mana, but something like heart is also very good.
