Early Game Strategy
Well seeing as you are the carry of your team, your gonna want to go top and take all the cs, if there is a solo lane, you know what to do your solo sejuani show that fake imposter who's the real boss of the top lane!. you should always run at your opponent to scare them, then freely farm minions while holding them out of exp. range. when your jungle comes up to gank always initiate, Piggy charge in and make them wish they had never played by slowing them over and over and if they have any hope left inside of them throw your ulti right at them to reassure them that they are not superior, they are in a game with Carry Sejuani!.
Mid Game
After your top opponent is emotionally drawn and has no self confidence, destroy his/her tower to make them feel even worse (always remember to enforce your role of superior carry). once top tower is yours, just start to roam, make your way through the jungle and always take wrath's when you can, gank mid when ever possible, make sure you have your ulti for a guaranteed kill. keep roaming and make others aware of your superiority over the game, your opponent at top is so emotionally destroyed he/she cannot even push properly so just go up every now and again to check on them make them feel even worse and destroy any hope of winning. Make sure to show your true power and kill anyone who needs to be taught a lesson by the one and only carry Sejuani.
Late Game
In the later stages of the game your opponents will break down into tears when they see you and turn and run in tear's. this is when you start to invade they're jungle and take everything (give blue to your mage). after a full jungle sweep go back and stock up on the vitals make sure to ward to keep them under surveillance. Don't want any *****es escaping today. go around in a pack, or with a buddy, at this point in the game they want you dead for all the trauma you have caused them. but just hang back and charge and destroy as always, this will end up in a surrender, or just a full out afk in base. SEJUANI CARRY FOR TH WIN! <3