linky
http://www.leagueoflegends.com/board...ad.php?t=28385
also, linky
http://www.livestream.com/kijik/vide...8-85a198929dca
gameplay vid.
basically your survivabiliy lies in rift walk, not in items :P, sparing rod of ages.

Stack RoA, kill before you get hit, run like hell.

Rush rod of ages from catalyst. Play conservatively and always know how much damage you can do with your spells compared to the opponent's hp, especially early game.

Because when you blow all your mana and the opponent's not dead, odds are you are.

Hence, keep harassing to a minimum so that you have killing power if an opportunity presents itself. If you make it to lvl 6 with a couple kills and no deaths you're in business.

I really don't think items matter too much past RoA and its always a game by game decision for me. However, you will need some sort of mana item after either catalyst or rod of ages; I like to get tear of the goddess but others work.

Afterwards, I alternate between getting archangel's staff, mejai's soulstealer, lichbane, banshee's veil, frozen heart, and rylai's scepter after RoA depending on circumstances. If you play him enough you'll know when you need which items.

What makes Kassadin successful is how you play him, which is a careful early game, aggressive ganking mid game and caster like late game being sure to rift in and out of combat as much as posssible to divert opponent attention and keep yourself alive.

I think Kassadin requires more practice and enemy consideration than most champions do so just be patient and practice.

Kassadin can be played in several ways.

You can go burst, which means sorc boots, deathfire, tear, Void staff, zhonya, archangel, lichbane
Summoner skills are ignite and exhaust, 9/0/21 build, magic pen runes predominantly.

Or balanced build, meaning boots of choice, catalyst, rod of ages, catalyst, rod of ages, zhonya etc
Summoner skills can be of your choice, runes should be magic pen marks, dodge/hp lvl seals, mana/lvl glyphs and HP/1 quints - 9/0/21 build


Or any mix in between as you see fit.



Tips:

Golem buff is very important
Solo lane = max null sphere first
Dual lane = max force pulse first

I have been using Kassadin pretty effectively going with AP and either mana or mana regen. My main weapons are Null Sphere and Force Pulse (the slow is invaluable). I find Riftwalk doesn't work well for dealing damage as it puts you right next to people, and Kassadin is to squishy to go very long at close range, especially against a DPS champ. I find Riftwalk is most useful as a chase/escape tool. With some cooldown reduction runes and items (such as Frozen Heart), I have gotten Riftwalk's cooldown down to 2.5 secs (if I remember correctly), almost making me uncatchable and inescapable.

Items (in order of when I get them):
Mercury's Treads - this is really helpful at keeping you mobile, cutting slows/stuns/etc. almost in half.
Mejai's Soulstealer - AP + Cooldown Reduction (if you can kill enough heroes) + cheap = Win
Archangel's Staff - high AP and mana regen, and passive increases your mana pool a ton, since you'll be spamming spells like crazy.
Nashor's Tooth OR Frozen Heart - big cooldown reduction for both. Heart gives good mana, and armor makes you a little less squishy against champs like Yi. Tooth gives good AP and Mana Regen, with attack speed as a bonus.
Zhonya's Ring - Massive AP + good mana. Big power boost.

Last item is optional, might want to get earlier depending on item. a few good ones (by no means complete): Rylai's Scepter, Rod of Ages, Lich Bane, or get a second Archangel's Staff or Zhonya's Ring

Last note: get Cleanse. Really helpful in escaping.