Look for any chance you can get to poke and get a few autos in to collect souls as your damage growth entirely depends on that. Grab any souls you can from minions and stay as safe as possible if your support [or adc] makes a play try your best to play off of it but be wary that dying 1 for 1 is never worth it as Senna you need to safely scale and snowball early as much as possible. Backing and getting double long swords into boots whenever you have the chance. Double longswords allows Senna to keep up or even out damage the opponent early depending on how many stacks she got before the first back. She has no AD level growth so she relies heavily on souls and gold to make up for it getting double longsword early in this build allows her to remain strong enough to trade blows with your opponent. Boots is equally as important as she is highly immobile before her items and this allows her to grow stronger offensively and defensively so early boots are a must. If you are ADC finishing cull and collecting souls is your main priority you must not die at any cost relay this information as soon as possible to your teammates and hope they will understand and protect you. Senna ADC is reliant on gold as she is on Souls so picking and choosing your fights are crucial for Senna ADC as opposed to Senna SUP where she wants to constantly trade. If your support has a good opportunity and you agree go for it and best case scenario you get a double kill and plenty of souls from it. Worst case scenario you both die your lane gets frozen and you lost a wave or two you lost plenty of souls and the opposing team is one step closer to getting upgraded boots which Senna always wants your vulnerability is now doubled. Keep that in mind that the worst case scenario is ALWAYS more impactful than the best case scenario.

In the transition period where objectives are spawning whilst in Lane you need to heavily rely on your support to help push lane and ward as Senna's wave clear is heavily gated behind her mana costs early. Instead of playing close to the dragon pit for dragon and dps'ing the objective try to stay as far away as possible warding off any potential threats with your long range and CC if your DPS is completely neccessary have your flash ready and stay on the walls of the pit where you can flash through the wall safely if the fight is winnable stay till the last minute but hover as far as you can using your range and supportive abilities to win your team the fight but at ALL costs preserve your life and go back to wave immediately. Make sure to collect any souls dropped by objectives and jungle monsters your jungler drops as it is almost always worth grabbing a few souls just waiting 1 or 2 seconds for them. Once your first item is completed and you have your ult you are pretty much online to start playing much more aggresively trying to push the wave constantly to get the tower and look for roaming opportunities and masssive value on your global ultimate racking up any kill and assist gold you can to help you further snowball. Keep in mind this is also when the junglers will be their most active as they are now on their first items and have their ultimates having your jungle mid and support work cooperatively to effectively keep you safe is crucial.

By this time you should have 60+ souls and finished cull and have had your second and third items. Now you are immediately a step above the rest if you are ahead this is crucial to now start limit testing and asserting pressure throughout the whole map. Roaming to towers to help siege running down anyone who doesn't respect your 660 range and 100% crit. If you see a immobile champion that scales shut them down immediately and continue to harrass them. This goes for Kayle, Asol, Nasus ETC. Match their wave clear and push towers as hard as you can to ensure you have priority for objectives and to make it harder for them to match your late game. Keep your eyes on the map constantly making note of your teams health their positioning and the enemies as well. Whenever you're on a timer for objectives play with them and walk around with a tank use your 660 range effectively and fish for any kills you can get. Don't push your boundaries too far you will feel agile and strong but in reality anyone on their team 100-0 you in the blink of an eye just as well as you can to them.

This is the time for Senna to really shine at this point she has superior range, damage, mobility, and utility to help the team accomplish anything. Your lack of defenses is still a downside so make sure to stay in your comfortable range of engagement without risking your life. Push lanes hard then play around any frontline you have and reign down your full build onto them you can deal damage and support your team at the same time offering the damage of a traditional ADC and the combination of peel CC and utility of a support. Play for Baron and Dragon hard Senna is strong and is now the main focal point of the team giving her Elder and Baron truly makes her unstoppable.