This is basically the mid strategy I use when I go mid with Xin, and I can assure you, you WILL do first blood at lvl 2. Harass hard the first time you see your opponent, then get creeps until lvl 2, then go in for first blood. Do not use any summoner spells until level 2. Because of your heal summoner spell, you can (if necessary), tower-dive your opponent.

When your creeps are attacking the tower, go back to wraiths and kill them if your team does not have a jungler. If you do this correctly (keep killing the champ in mid, he will not stand a chance) you will be at lvl 7, when he is at lvl 4. Therefore, you will get fed, and game is yours ftw.