Do not pair Senna with another ranged AD in the bot-lane.

Senna needs to trade/be aggressive in lane in order to scale properly. Pair her with a champion that has lane presence and poses a clear threat to the enemy. Typically, she goes well with high-CC or high-damage mages, which still scale into late-game carries.

If playing a build with slows, you can potentially pair with a high-CC melee champion. For example, Glacial Augment goes well with typical cheesy melee bot-laners such as Sett, Pantheon, and Jarvan IV. This strategy involves catching your opponent off-guard in lane and snowballing the game.

If unavoidable, try to at least pair with a traditional ADC that deals magic damage, such as Varus or Kai'sa.

Many pros and high-elo players take AS because the best ADC mains have an AS-oriented play-style (from playing that way for many years) and are highly effective with a little bit more AS. Additionally, Rapid-fire Cannon's bonus range provides a way to safely poke and gather souls against highly skilled opponents.

The average player should focus on AD, Lethality, and MS. Senna does bonus AD on-hit, as well as bonus current-health damage in intervals from her soul mechanic. Additionally, she must trade in bursts throughout the entire game to gather souls and scale correctly. This means that high AD and kite-ability are core to Senna's kit. If her standard combo (A+Q+A) if performed correctly with good animation cancels, there's no need for bonus AS.

You do not need 'Presence of Mind' unless you are building Muramana. Take 'Manaflow Band' and 'Celerity' instead. 'Celerity' synergizes with many core parts of this build, such as Black Cleaver, Senna's MS on-hit, and 'Approach Velocity'. The bonus MS will make Senna extremely slippery.

There are two ways to play Senna: as a physical damage carry and as an all-around carry. Playing as an all-around carry is standard while playing as a physical damage carry is situational i.e. only when the team comp demands it.

Depending on how badly the team requires a physical damage carry, adjust the build in these ways (top to bottom, first to last resort):
- Build Muramana and take 'Presence of Mind'
- Build Infinity Edge
- Replace Umbral Glaive with another Lethality item
- Replace Black Cleaver with Lord Dominick's Regard

You may want to consider smurf builds on Senna if you are:
- always filling the physical damage carry role because you've been carrying this way for millennia
- love the feel of AS on ranged champions and don't require the extra AD on Senna because you are just that much better than the opponent
- love cheese

If you are "smurfing", consider taking items that the pros (who play by "feel") take. Rapid-fire Cannon will make it easy to harass and gather souls at range. Runaan's Hurricane lets you pull 3 souls at a time from enemies, as well as reducing your Q cooldown by 3 seconds instead of 1 second per auto.