This build is somewhat of an oddity. When I was playing Nami I realized that her kit makes her uniquely suited top laning and then transcending into a support/Spellblade Assasin. When I started to try this out, I got a lot of lashback from my teams in champion select, but the actual game was extremely enjoyable.

I put this build up mostly so others could see it and comment on it. I'm not a perfect player, and I assume that a lot of other people could have some insight into how to improve it.

In the early game you have to play relatively aggressively. Constantly auto attack your enemy, and then Ebb and Flow them to heal yourself up from any minion hits you receive due to this. Personally I Ebb them whether or not I have taken damage, and just continue using it to pound them into the ground until they have to leave lane, which tends to be rather early. You are going to have to have a lot of trouble killing them early game, though if you land a bubble and use tidecaller's blessing it is still possible.

It is key to understand the use of Ebb and Flow. Make sure to use it when you are going to be within bounce radius, either to heal yourself from the bounce off them or to hurt them with one of yourself.

This is going to be the somewhat frustrating part of the game. Though any single character is going to have significant trouble killing you, your damage simply isn't high enough to be considered truly dangerous yet. Keep your team alive, and maintain constant ganks taking as many as possible with your tidal wave, and you will easily have the gold to come into your power. Stay in the back of teamfights though, a mix of a carry and support mindset. Know who to use your abilities on.

Con's
-Nami is squishy. If they don't nuke you, then you won't die. But that initial nuke can really ruin your day
-You come into your own later than most people prefer. A significant proportion of your gold is going to come from assists, but you have the capability to get on the order of 30 of them a game, easy.

Pro's
-You should be able to win almost any lane because of your constant use of Ebb and Flow
-You are extremely versatile if you build right. You have the option to go AP, Spellblade, or simply utility. Few characters outclass a top Nami for that trait.
-While dumping significant single target damage with melee attacks, you still have your bubble and ult for large teamfight disables(Don't throw away the bubble early!!!)

This was a build I put together for the point of review. It's completely against the meta, its weird to play, but its tons of fun. Just saying, I am a support main, so I enjoy playing a top that can transition to a partial support and partial DPS role. So don't hate on me just because you like more aggressive top laners =D

If I get interesting feed back, I'll fill in this guide a lot more. Runes really depend on exactly who you are facing, and any lane you are going to face depends more upon the rest of the team than exactly who is opposing you, so I didn't bother to do a full analysis yet

Hope you enjoyed the concept