I played Nami for a long time on botline like support. In the course of time, I have put her strength in the fight 1v1. Just know how to use spells and be accurate. Her W offers damage to opponents and heal for allies at a relatively long distance. Although the bubble is not easy to hit, but if you have enough experience, you can stop your opponent from attacking and defending. Her E can slow down the opponent - Good for a
easier hit of a bubble - good if an opponent tries to escape and you have a cooldown on W or Q - Good if you yourself escaping. He R is good for both teamfight and for fight 1v1. You can use R as the start combo or the end of combo.

LVL 3 COMBO

From LVL 1 use W for poke damage and heal you. The next time is W can do the most damage to the enemy and also heal your wounds. If the opponent has about 50% health on lvl 3 use this combo. There's a great chance of killing your opponent. If the opponent has more healt than you do not risk the combo without the help of a jungler.

E - AA - Q - AA - W - AA - Ignite
E - AA - W - AA - Q - AA - W - Ignite

LVL 6 COMBO

Combo on LVL 6 is similar. But using R is more powerful. Use R + Q combo knokup the opponent for a long time. When you have enough time to use W - E - AA - AA - AA and then reuse E

R - W - Q - E - AA - AA - AA - W
W - E - AA - Q - AA - AA - R - W

Pros
Tons of damage on combo
So many CC
DAMAGE + HEAL

Cons
It's not easy to farming
Hard to escape without skills - Unpossible to escape without mana
kill or be killed