Kleptomancy is the biggest meme of a mastery riot has ever put into the game. Early game with klepto is insane because you generate a crazy amount of gold so you can finish your build faster. When fully stacked, Rod of Ages is one of the most gold efficient items in the game, meaning if you do well in lane you can easily have your rod of ages fully stacked by 20-25 minutes in. This keeps you well ahead of the curve while you are building into less efficient items like luden's echo and lich bane (these are good because of their passive effects, not base stats).

Q - This is Nami's best ability for making picks on enemies. If you have a good team for invading you can get an easy kill off from this ability alone. Late game if somebody is touched by this then they better start sorting out funeral plans because they're gonna have a lot of time to contemplate death while they are inside that thing.

W - Make sure you are using your W correctly, if you are in a 2v2 situation then this ability will make or break the fight. If you W an enemy it will bounce to an ally then to an enemy again. While if you W an ally it will bounce to only one enemy then heal another teammate. This ability will not bounce to the same person twice, so keep that in mind when trying to maximize damage.

E - This ability is crazy good when stacked full AP. When you are full build you will be adding an on hit slow of about 50% to your target's autos. Your ADC is gonna love you if you use this properly because of the amount of damage and cc you can add to their autos. In lane you want to be using this to proc your kleptomancy to get your early items.

R - Use your ult to engage, disengage, lock down people with a Q-R combo or whatever you want. Nami's ult will destroy the enemy team if you use it in a corridor in the jungle or something. Allies that stand in your ult will get the movespeed buff from your passive, you can use this to your advantage when chasing.

Passive - If you need to speed buff yourself or an ally then use an ability on them, it's that simple. If you are chasing somebody solo then ONLY use your E to chase as your W will lock you into place. If your ADC is chasing somebody down then use your W on them because they don't get locked into place like you do. Your passive is what makes it so easy to proc kleptomancy on people, because when you E yourself you get a huge movespeed steroid you can use to get a free auto off whenever it's up.

Early game you're gonna want to proc Kleptomancy as much as humanly possible. Getting gold is very important for this build. Sell all elixrs you get unless they are sorcery or rogue.

You won't be buying sightstone early on so make sure to manage your wards effectively. Kleptomancy can give you wards sometimes so use that to your advantage when you can. If you get a control ward from kleptomancy then do your best to guard it, you can get a load of free klepto procs if they try to take it.

You need to be as aggressive as possible, make sure to let your adc know that you're gonna be slapping your 20 inch fish **** all over your opponents like the alpha male you are so they know to follow up.

Stick with your ADC and try to make as many picks as you can. You won't have much solo kill potential until you have lich bane and luden's so you need to be helping around as much as you can. Getting a gank off mid with your ult can be devastating for the enemy team due to how much damage you can deal.

Continue to stack as much klepto whenever possible.

This build has some 1v1 potential in the late game, but I'd recommend sticking with your team still as you will be a god for setting up kills for your carries, being able to burst someone down to 25%-ish health while keeping them locked into place with Q+R and then keeping them slowed with your E is crazy. Nothing will escape. If you start to lose a fight then try to use your ult to disengage and make sure to be poking and proccing klepto. You can get 250 stacks for athenes very easily with how much AP you have so make sure to get maximum value out of it.