Gladiator's Shield is an early game solo lane item that has more recently come to light in the meta. On Nike, this item is great, as the stats favour her greatly (particularly the CDR, much needed) and it provides some additional sustain to her kit, with the passive HP5 already coming from her 2.
Nike is a mana hungry goddess, and Ninja Tabi responds to this need efficiently. If you want the bigger power spike,
Warrior Tabi is an option, but you are sacrificing a lot of sustain, and if you have a mediocre jungler who does not do mana camp for you, you may be left distraught.
One of Nike's downfalls is her hefty cooldowns. Enter
Jotunn's Wrath, providing 20% cooldown reduction, along with power, penetration, and mana. This item is good, period. It works on almost all physical gods, and is just an overall great item. The cool-down reduction is essential for Nike, as already stated.
If you haven't already, at this point in the game, you will likely be rotating out of solo to come and help your team in teamfights and securing objectives. Spirit Robe gives protections to help cope with the magical damage on the enemy team, and the final bit of cooldown needed to push Nike to max CDR. The CCR in both the pure stat itself and the passive is also very helpful and potentially life saving.
Mages are designed for the late game (typically) and Nike is going to be at the forefront of the battle, being the solo laner. Due to this, absorbing damage whilst still putting enough out can be tough. I haven't seen much Runic Shield and I don't know why, because it's such a great item. It's cheap, the stats are super helpful, and the aura is impactful to say the least.
Of course, Titan's Bane is required. This item doesn't need much explaining, but just to clarify, the percentage penetration is most effective in the late game, and being able to actually damage the more tanky characters on the enemy team is made more possible with this item.
Devourer's Gauntlet - "not necessary with her since she gets additional HP5 from Plan of Action which helps alleviate that a little bit" - I completely forgot about this! It would make more sense to build HP5 than lifesteal if anything.
Blackthorn Hammer - "I think there are better items for her." - You're probably right. The main reason I choose to build Blackthorn Hammer is because I'm not a good player. Supposedly, Nike is one of the easier warriors, so I made this build forgiving to players, at the cost of slightly better stats. I think I'll add in an alternative for stronger players.
Hydra's Lament - "I wouldn’t use this and go for more penetration in the build like Titan’s Bane" - I build Hydra's just because it's one of the few items that provides cooldown and power. I understand building her as a bruiser opens up many more sources of CDR (e.g. Breastplate of Valor) so I'll have to look into this when updating the build.
Hide of the Urchin - "I just don’t like that you put it last" - why did I put it last? It was 4am when I made this build, but I absolutely agree that building this item last is ridiculous! Why did I do that... 😂
The Crusher - Yeah, I like the Crusher in general on Nike. It just works, granted the other stats have been covered. It's not something I would rush to build but it works.
I'll give you a shoutout in the build update. I'm working on some visual changes along with item changes. Thank you so much! ^-^