Not sure about the others, but as for Master Yi I find the online guides to be mostly trash. I like going adc yi mid as much as I can and I get scores like 34/12/12 doing it.
For Yi I usually start with Berzerkers, then I move onto Ionic Spark. I get Spark because it's just better than Phantom's Dancers. Spark gives you 50% attack speed, 250 hp, and 125 damage to 4 targets every 4th basic attack. It's practically the same attack speed as Phantoms, minus the crit chance and bonus to movement speed, but gives you hp and costs less gold so I think it's a way better choice for early game. With Highlander you'll be moving and attacking as fast as needed anyways. Also, spark gives you the extra damage every 4 attacks while Phantom's doesn't actually give you attack damage. You'll be doing more damage with the spark than you ever would with the 1/3 chance crit damage, and since spark is magical damage, you just made Yi a mixed damage dealer! After that I get 2 vampiric scepters. They only cost 450 each so you can get them really fast as well, especially since you save around 700 gold for getting spark rather than Phantom dancers. The 20% lifesteal helps you sustain better in lane too since yi has no healing but meditate. Meditate is useless frankly and you should never go ap yi build since you only have a single ability that actually deals damage while your e and r both add onto your dps, improving your lifesteal greatly. Once you get your 2 scepters, then you want to focus on your investments. You first want to buy a B.F.S. Your next purchase after that will be another B.F.S if you can afford it the next time you visit the shop, or a BloodThirster if you can't quite afford the second B.F.S. The reason you want to eventually get two BloodThirsters is because they deal more damage maxed out than the infinity edge, and you'll have +40% lifesteal making you very sustainable. And guess what? Yi's great at mashing those minions, especially since he has the spark! So leveling up your BloodThirsters is easy and quick. Your fifth item you'll want to get is Warmog's armor. It gives you tons of HP and also powers up as you kill minions. Last but not least is your 6th and final item. Guess what? This item can be whatever you need for the occasion! Quick Silver Sash, Frozen Mallet, some more magical or physical armor, etc. Whatever you need for the late game!
So there you go. A good build for Yi that keeps progressing stronger and stronger as the game goes on(which is good), no huge investments until mid-late game, costs anywhere between 3k-6k less than other online Yi builds, leaves the last slot open for whatever you need for the occasion, offers great sustainability mixed with high damage output, high damage+high health+high life steal makes you perfect for backdooring, ganking, tower diving, chasing people down, teamfight striker, minion wave masher, jungler, etc. Also helps you survive longer/fight more after you've been cc'd.
TL;DR Berzerker Greaves, Ionic Spark, BloodThirster, BloodThirster, Warmog's Armor, whatever you want.
Edit: I also have some helpful tips when playing as Yi that'll make you way more effective.