for 12.12 i regret to inform you guys but for now leathilty senna is practicaly unplayable she is terrible one day we will come back now with 12.13 its getting pretty sad they wont stop senna is just getting **** on currently look for another build with crit but really thats bad also

If you guys like this guide make sure you follow my twitch I stream league almost every day mostly playing senna and I would be thrilled to help you more there.
https://www.twitch.tv/silentoe_

Hello my name is maddog I have been playing since season 7 and am most recently a gold ranked senna bot lane main. I have a ton of play time on senna and absolutely love the champ. Senna just has such a fun and different playstyle form any other champ I love being able to do massive amounts of damage per hit while still having a fun kit with stuns healing and speed. I love sniping kids across the map with my ult and enjoy staying occupied at all times of the game trying to farm my passive.

Pros

does a lot of burst damage
has great cc
has a god heal from a=q while also doing damage with q
Has one of the best teamfight ults in the game
Has great infinite scaling ability
Looks great (Especially with the prestige skin)

Cons

Super squishy
Kinda slow if you dont have your e or Ghostblade
Long cooldowns
Passive got a pretty big neft to critical strike recently
Hard to recover when losing

Early Game

Basically early on you want to focus on getting stacks and increasing your CS. You seldom want to hard go in for kills you many just want to poke for stacks without putting yourself in danger. The only kills you want to go for are ones that you are certain you will get and only when you have cc cooldowns up.

Midgame

Your main goal here is to again get stacks and make sure you continue to not die it is very important that you do not feed about this point you will start getting some items and your stacks will be getting high so this is when you want to start fighting but it is very important that you let your team peel for you and never frontline or 1v1 one because you are so squishy.

Lategame

You just win late game make sure you are in ever teamfight. If you play with your team and they peel for you you can dominate the game because at this point you will have a ton of range with your stacks and deal a ton of dameg along with having a ton of utility and your ultimate cooldown should be low enoght you will have it every teamfight. But still remember try to stay away from 1v1s unless it is a super squishy adc or support and you know they are alone cause senna is super squishy at all stages of the game. But at this point you should have at least a lot of mobility from ghostblade and your e so that will help.

Some basic combos that I like include the easiest one for getting stacks early game is using an auto-attack to proc glacial augment then hitting them with your q it is super simple and effective. Combos for teamfight include mainly just w>Q>R and also just w auto q.

Since Senna has such long cooldowns it is super important to be very thoughtful when using your abilities. Early game it is important that you are always aware of what abilities are available for instance you want to make sure that you have your e available when you push up because that is your only way of getting extra mobility. You also want to make sure of things like you have your w ready when you want to go in make sure you ping that constantly to help your support know when a good time to go in is. Also, it is important that you know how your q works that when you auto-attack it takes a second way from the cooldown use this to your advantage when fighting and also just poking. one final thing is to make sure you get good at aiming your q through minions teammates and wards to try and hit enimeis with.

Obviously, if you want to watch me I would say I have pretty decent mechanics but I will always help you and guide you in the right direction you can do that at https://www.twitch.tv/silentoe_
Some other great things to watch would be a lot of games from worlds 2020 there is a ton of senna play as an ADC and there is a lot of great things to pick up from those excellent players.
Other streamers you can watch for senna gameplay include rommmau or sprount