If you're top, I don't always recommend magical footwear. Many tops can just run you down because they have higher base MS and will buy boots while you're still waiting 12 minutes to get yours; if they get phage you can no longer farm in those cases. Being able to get boots+aether whisp can be a lifesaver vs garen. If you're mid, it should be fine in most cases, though.
As far as itemization, most of the time you're going to want to back when you have 1700g, if you're able to wait that long. You get 
at that point. After that, if you're ahead, just head into 
when available, or 
depending on what you need. If you need MR, don't always finish protobelt unless you absolutely need the waveclear/displace; go into SV after deathcap or spellbinder, or 3rd+ item if you can wait that long. If necessary, don't feel bad for finishing protobelt+zhonya's first. Sometimes you have to in order to safely farm, just don't expect big damage for a while in those cases. DO NOT BUY SPIRIT VISAGE UNLESS YOU NEED IT. IT HEAVILY GIMPS YOUR DAMAGE COMPARED TO PROTOBELT OR ANOTHER AP ITEM.
For runes you should generally be taking phase rush, with nimbus cloak, transcendence, and gathering storm. Secondary should usually be magical footwear and cosmic insight.
For general gameplay, don't always E when you're low before an empowered Q. That .25 second cast time makes you die before you get it sometimes. In some cases its better to empowered Q THEN E so you actually survive until empowered Q.
You can E BEFORE you W, but you cannot start E during W. Try to always E before you go into pool unless you're using it to avoid a skill shot. Also, don't be too trigger happy with W. Its got a long CD and takes 20% of your current health.
Learn what you can get away with when phase rush is activated.
Use your empowered Q to zone during laning. Wait until the last second to use it on a minion if you can't Q them. Don't push too hard trying to do this, though. Freezing is still important.
Remember that W and E during their charge/duration drastically slow your bloodrush decay. Use this to your advantage. Zhonya's completely freezes the decay.
If you're charging E, using R will instantly release this. You can time this to deal damage with E+Q almost instantly while buffed by R.
Don't forget to auto attack when going for a kill. One or two autos is often the difference between someone living or dying, especially early game. Autos are also buffed by your R.
E slow can help a lot when kiting away from some champs like Garen or Udyr. Get used to timing it well, as it starts to slow YOU after it gets to the charge point where it inflicts a slow.
Only charge E for 1 second. It charges up to 1.5 seconds, but you gain no additional benefit after 1.000000001 seconds outside of zoning.
You don't always have to fully charge E. Remember that it takes progressively more health the longer you charge it. There are cases where it may be more beneficial to not consume that HP or just release earlier.
While under turret, for the first 10 or so minutes, tapping e AFTER melees are dead, you'll only have to auto once after the turret hits a caster minion. Basically, for melees 2 turret hits + 1 auto/e for last hit. Vs casters, 1 turret hit + 2 autos or auto/E will get the last hit. Try to set minions up to be easily farmed before it comes their time to die.
If you want to empowered Q after zhonya's/pool, don't always try to do it at extremely low health. You'll come out of pool/zhonya's and most of the time die during your empowered Q animation. Try to have enough HP or distance as buffer during those high risk moments.
Don't be afraid to go Predator as your keystone if the enemy team is hard to flank or move into.
Finally, practice last hitting in the practice tool. A lot. Farm is extremely crucial to staying relevant. A vlad that's behind has a VERY hard time recovering. You NEED to hit your item timings or you will fall on your face every game. Try to hit that 100 farm in 10 minutes a few times, then put it into practice in pvp games without dropping CS while you interact with your enemy laner.
