Although you won't be building the same items every time, this is an example build that's pretty strong
early game core items:
- this gives you basic hp/mana regeneration for self sustain, and also makes you deal more damage to jungle creeps. It's a cheap item that will build into the spirit of the ancient golem later, so try to at LEAST by this item on your first back!
- if you got couple successful early ganks off, you might want to invest in these early. These will let you roam a LOT faster, and also make multiple enemy lanes feel like you're always there. In addition to your Q to dash through walls, you should be incredibly mobile.
mid game core items:
- This item is like... SO good on sejuani. Not only will you be able to deal more damage to monsters with "butcher," but it gives you a LOT of health (which means W deals more damage) and cooldown reduction ( more dashes, more ultimates!). And as for the cherry on top, it gives tenacity - which means you won't need to get mercury treads for the cc-reduction.
- I only recommend this item if you're snowball really hard from early game leads. This item gives health (again, more damage while making you tankier) AP (all your skills scale off AP) and magic penetration (which means you will be dealing almost true damage to squishy carries mid game!) And.. no matter how much I think about it, every stat on this item is great on sejuani in order for you to snowball. Your skills will start to deal MASSIVE damage (at least before the enemy gets some mr) and you will be not just a tank.. but a SUPER TANK!!
- take sorc shoes if you went haunting guise build for the insane amount of magic pen you get, meaning you'll be dealing a lot of damage. Otherwise, if you didn't opt to go mobi boots I recommend getting ninja-tabi's because these will lower the AD damage you take by a LOT, especially the AD carries who auto attack a lot.
late game items that you might buy.
- Against double AP, or if the enemy team has multiple catch abilities like thresh/blitz/nautilus hooks or a lot of pokes like nidalee/jayce, you might want to invest in this around late game when teams start grouping and sieging. Getting this will not only make you slightly tankier, but it will let you soak up pokes for your team (although you shouldn't just blindly do it and waste your banshee bubble).
- I personally don't like this because I think a lot of the money you pay for mana on this item is wasted. However, if you're against multiple auto-attack dependent carries (this goes for some AP champions too, like kayle) you should get this because it gives a LOT of armor/cooldown reduction, as well as that handy aura that slows attack speed.
- If you feel like you're just dying way too much, or the enemy team seems to be a completely single target focused team, then you should get this so that you can dive in without the fear of dying.
- a great item to get early game before bulwark if you're against an AD heavy team. The AOE shield is also pretty strong early-mid game. Once again, cooldown reduction is nice to have on sejuani because it benefits literally all your spells.
- this is one of the best late game items against heavy AD teams. It'll pretty much make the enemy AD be scared to hit you because it will slow him. Remember to use the active on as many people as you can, on top of your already huge slows this will just make everyone a little turtle trying to climb out of the sejuani train.
- I like to get this against.. stuff like tryndamere who destroys me everytime. Yeah. Tryndamere wouldn't attack me anymore if i had it. I'd also get this against an AD carry who decided not to get lifesteal for some reason, as it'll do a lot of damage back to them and they wont be able to sustain themselves.
- I personally like this because it lets you waveclear/jungle clear faster. Especially if you took haunting guise / sorc shoes the magic pen applies to the sunfirecape fire, so it's pretty neat. This gives you both offensive/defensive stats, and is one of my most favorite items in the game if you feel like you want both.
- Not too practical, but if you have a double AP team and none of them gets an abyssal, this is pretty sweet in conjunction with the 3 of you in terms of the free magic pen aura. Otherwise, I don't recommend it. I know you can get this with haunting guise + sorc shoes for insane magic pen, but really you'll be too squishy and it's really not practical.
- I like getting this as a 4th or 5th item if I'm pretty set on just being that HUGE BOAR in front of my team that will just soak in ALL the damages. If you have a bulwark + warmogs you should be tanky enough to last in teamfights for an extremely long time.
- This items better than the yellow trinket on junglers, because you're going to be roaming all over the map all game. So buy this when you feel like laning phase for most lanes are over and you're able to freely clear out areas to start pressuring the enemy team.
Example build against double AP:
example build against heavy AD:
use your intuition and decide which item to get as the game goes. For example if the enemy AD top gets fed early you're gonna have to change your build up accordingly, favoring early armor.