A quick guide to boot enchantments

Boot enchantments aren’t very powerful. For their cost, they don’t need to be. The cheapest only cost 475 gold, and the most expensive cost 650 gold. Each enchant gives a buff relative to its cost—small but not insignificant. Because some of their effects aren’t easily noticed or as “sexy” as damage or health, boot enchantments are rarely purchased until a player has already completed his or her item build. But boot enchantments shouldn’t just be an afterthought. So, which boot enchantments are the strongest? When should they be purchased? And what type of champion should buy each one? 

Alacrity

Passive UNIQUE - Alacrity: Grants +15 bonus movement speed.
Item cost 475 gold

Who should buy it? Anyone who doesn’t benefit from any of the other boot enchants.
Is it worth it? Yes. Movement speed is a very difficult statistic to itemize for. Alacrity gives roughly the same amount of move speed as Movement Speed Quintessences do.
When should I buy it? You should buy this whenever you’d value movement speed over damage or defense. If you think you lost a team fight because you were too slow, buy this upgrade. But keep in mind that Alacrity is the same cost as a Health Crystal and a bit more expensive than a Long Sword.

Furor

Passive UNIQUE - Furor: Whenever you deal damage with a single target attack or spell, you gain 12% movement speed that decays over 2 seconds.
Item cost 650 gold

Who should buy it? Attack damage carries, for kiting; champions with a spammable single-target ability, for chasing.
Is it worth it? On some champions. For 175 more gold than Alacrity, Furor gives roughly twice the bonus
to movement speed, but only if a champion attacks or uses a single-target ability every second or so.
When should I buy it? AD carries shouldn’t be afraid to purchase this early. If you’re playing against champions that can be kited easily, like Udyr or Darius, it’s worth buying after Zeal for a huge buff to your movement speed (because upgrading to Phantom Dancer doesn’t give any extra MS).

Homeguard

Passive UNIQUE – Homeguard: Whenever you are at fountain, you instantly gain full health and mana, and gain a 200% movement speed boost that decays over 8 seconds (4 second on Crystal Scar). The bonus movement speed is lost upon entering combat. The effect cannot activate while in combat.

Item cost 475 gold

Who should buy it? Players that want to be able to heal instantly after returning to fountain or stop enemy champions from back dooring.
Is it worth it? Yes. Homeguard allows teams to go for objectives like Baron while quickly responding to defend their own base because of the speed bonus and instant healing. It’s also strong against siege compositions that are pushing your base because you can heal instantly at fountain and jump right back into the fight.
When should I buy it? Homeguard is possibly the best late-game boot upgrade. It’s also powerful on junglers with other move speed increases (like Rammus, Hecarim or anyone with Boots of Mobility) because they can go from the item shop to the middle of the map in seconds.

Distortion

Passive UNIQUE – Distortion: Decreases cooldown of Ghost, Teleport and Flash by 25%.

Item cost 475 gold

Who should buy it? Champions with abilities that synergize extremely well with Flash (Morgana, Karthus, Skarner). Also, champions with both Teleport and Flash/Ghost who find themselves split-pushing.
Is it worth it? Not really. While having a shorter cooldown on Flash would be very helpful during the laning phase, the upgrade can’t realistically be purchased until later. The longer the game lasts, the less important 75 seconds off Flash becomes. In addition, the other boot options offer actual combat stats, while this enchantment does not.
When should I buy it? This enchant is best on champions that are split-pushing with Teleport and Flash or Ghost, so buying it at that stage of the game would be best.

Captain

Passive UNIQUE – Captain: Allied champions running toward you gain 8% bonus movement speed. Nearby minions gain 20% bonus movement speed.

Item cost 650 gold

Who should buy it? Tanks with strong initiation abilities (Hecarim, Malphite) who charge in ahead of the rest of their team and supports who sit in the back of the team.
Is it worth it? On tanks and supports, yes. Tanks often charge into battle in front of the rest of their team. With Captain, the rest of the team can stay right on the tank’s heels. The enchantment works almost like a mini Shurelya’s Reverie. It’s also powerful on supports because it helps aid carries in fleeing from diving opponents.
When should I buy it? This is a purchase for the supporting roles (tank and support) to help their comrades in team fights. If both roles buy Captain, the rest of the team can get the 8 percent boost running either way in a team fight.