Welcome to the wondrous champion that is Nami. I'm WiLDxSerialKILA, I started playing league at the end of season 5 during the preseason of season 6. Using the AP Nami build I have a 100% winrate on Nami in solo/duo ranked. Because Nami is such a safe supports she is the best pick in my opinion.

Pros:

>Movement speed with any ability she casts on herself or an ally from her passive (Surging Tides)
>Good hard cc and early game harass with her q(Aqua Prison), if you land it
>Poke and sustain with her w(Ebb and Flow)
>Auto attack buffs for your adc with her e(Tidecaller's Blessing)
>Great team fight potential, or disengage with her r(Tidal Wave)
>Nami is a very safe pick and practically an uncounterable support with a strong early game

Cons:

>Really reliant on her cc
>Nami isn't very tanky so unless you have another tank you won't have a good front line
>She has low mobility, so you're pretty dead if you get cc'ed
>Not so great mid to late game unless your team is really ahead