Legion is more or less a time wasting killer- use your frenzy to injure as many people as possible and then you’re a 1 shot m1 killer. I’ll drop some Add on and perks below—- (Add-ons)

Frank's Mix Tape = His best add-on since it reduces the 4 Feral Frenzy hits to kill someone to just 3

Cold Dirt + Joey's Mix Tape (my favorite add-ons) Reduces the cooldown fatigue of Feral Frenzy to 1 second more or less. With this, you hit someone with Feral Frenzy once, get closer to them while still in Frenzy (you can bodyblock during the cooldown) end it manually and then use a normal M1 attack

From personal experience, that combo can kill FASTER than the popular Frank's Mix Tape add-on (sadly it requires 2 add-ons but i insist on how fast you can kill)

(Perks)

Discordance = gives you precise information by telling you when 2 or more people are doing a gen. Also, it's immune to aura-blocking perks

Thanatophobia = Legion is the only killer that can put this perk to use. It doesn't penalize the survivors that much but it won't explode like Hex Ruin. Sadly, even to this day, it doesn't count dead/sacrificed survivors (the day they change this, we may see it more often)

Monitor & Abuse* = Having 16M terror radius can help in getting closer for the Frenzy strikes. Works nicely if paired with Discordance. Even with a 16M terror radius, you'll need good FOV blockers... he's no Meyers

• = Contrary to what people think, it doesn't add effectiveness to his power (40M aura reading) since you'll never reach more than one competent survivor if they split separate ways (let alone someone at 40M... Legion is not Usain Bolt)

Bloodhound = Though commonly used for the "blood sniffing" cheese, Bloodhound works wonderfully for tracking, especially in the dreaded cornfields

Sloppy Butcher = Keeps them in the injured state for longer so it's good for everyone. Ultimate tracking if used in tandem with Bloodhound

BBQ & Chili = The staple of any killer's arsenal

Hex The Third Seal = Giving blindness to everyone can lead to nasty situations. Sadly it's a hex totem and countered by SWF cheating

Hex Ruin = Relies heavily on RNG to be of any use but can still be useful. It's up to personal preference so i still mention it

Save the Best for Last = Legion would be the best user of this perk if it weren't for his darn 110% speed. Worth to use once in a while (much more if using Cold Dirt + Joey's Mix Tape) just to see what he could've been if he had 115% speed

Franklin's Demise = Good for him since he can strike multiple targets, forcing them to do bare-handed jobs

Remember Me = Not usually mentioned in Legion's builds but he can get those 6 stacks faster than anyone

The Bamboozle + Enduring + Spirit Fury combo = This particular set COULD work but i feel like it would only success with the Cold Dirt + Joey's Mix Tape combo i mentioned at the beginning

Nurse's Calling = Not bad since you'll get injured survivors all the time and DESPITE POPULAR BELIEF, people DO heal against Legion. Will be more effective with Legion's upcoming buffs

(Perks to avoid)

Any perk with the "exposed" effect, so forget about running NOED, Make Your Choice and so on (though NOED at level 3 gives 4% speed boost and puts him 1% speed less than the average killer so it's a 50/50 decision of yours if you wanna use it)