I've been playing AP Rakan for over a few weeks now and it's currently the most enjoyable and unpredictable thing people expect. Playing him in top lane or even mid people don't expect your early game damage or even expect you to scale into the late game. The only problem with playing Rakan in general is that you only have two damaging abilities (not counting your ult). You have to only take fights where you know you can win or where you can evenly trade and wait for your cd's to try to kill them.

When starting off no matter what lane you are playing in you always start W LvL 1. Taking W allows you to either knock up your opponent and get a few hits off to have an early health lead, or allow you to escape from getting ganked by the jungle. At lvl 2 you always take Q. With Q it allows you to have some extra poke potential onto your opponent while also healing you for 30-50 health per hit. At level 3 I recommend taking another point into W, you should only put a point into E if your jungle is coming to gank and you're too far away to knock up your opponent.