Good build for a newer player.

I've seen people play with this build. Early game they are dominating me (if it's Karthus vs Karthus) because of their endless lay waste spam. Once I land some good shots they heal and my mana runs out and they use clarity. But once youre in mid/late game those two spells become useless. Get yourself a golem buff and u wont need clarity. Heal is another thing. Youre a nuker and it's all or nothing. It can be usefull, but when you get stunned your dead, even with your precious heal spell... It's harsh, but it's reality. I can see this build kick *** by dominating early game, get a lot of minion kills and kill the enemy a couple times. Against low ELO players this might work, but against high ELO players you wont get kills... You might want to keep health and swap clarity for flash or ghost to get away from ganks etc.

Finally a little tip on the skill sequence: The fastest way to up a skill is this: lvl 1-3-5(6 ulti)-7-9. So if you want to max out lay waste first you set those numbers ;)

Level 3 lay waste on level 4, now thats something i hadnt thought of before