Evenshroud is an underistimated item on Heca. The threat of CC gets lowered, because if you get CC'd you will deal more damage and on full engages you will deal 10% more damage. 10% extra on every Q with 0,5s cd and Muramana is a LOT. But it does not end there. Evenshroud is the cheapest Mythic in the game. This gives Heca a very cheap spike. This combined with the fact that it gives you A TON of resistances makes Hecarim an unstoppable killing machine.

There are two big factors in how to play Hecarim propperly besides the general know-hows. Sheen proccing and Q stacking. The latter I'll explain in the next header. This build is almost foolproof, because the only thing you'll have to do is don't take bad fights. With Sheen items you'll need to pay attention so you don't accidentally cancel your auto-attack with Q to proc sheen. Whilst not optimal to cancel your Auto-Attack your healing and damage does not rely on it. This build is primarely focussed on healing from W and Conq and damage from Q and Muramana.

Be ware. Don't just go in and fight any fight. Whilst it may feel like you won that previous fight and your ego is now through the roof. You won that fight because you got your Q stacks. With Q stacks you deal extra damage and obviously less cooldown. Do not underestimate how much more damage the combined two do!

So in short. Do not go into fights where you aren't 100% sure that you can kill if you have no stacks.

I found that on lvl 4-5 with no items you can fight just about anyone if you have 3 Q-stacks. There is a bit of a moment where you don't really go up in damage. This point is when you have Manamune and BC but Manamune is not fully stacked. Prioritize stacking Manamune and not dying (more info on this in next chapter). If you eventually get Muramana your damage goes through the roof. You're a monster by this point. This is when you build Evenshroud and the power of Evenshroud comes in and makes you an unstoppable tanky killing machine.

This should not be underestimated. Even if you have been doing good and got to the point of getting Manamune, if you int from here you are done. Manamune alone is just bad but that Muramana spike is big. Every Q from then on gets so much more damage. So do not int when you get Manamune. Try to stack it and do not go for fights if you are not sure you can win it. Even if your team flames you for not going in, it will reward later.

(This is why you build Tear first...)

In my opinion the most important thing in Low Elo is to play for yourself. Just think I'm playing with and against 9 other people with -50 IQ points. This is why you should almost always full clear. Learn to kite, keep your Q stacks up and you should be able to full clear before scuttle has spawned.

Example from Inori: https://www.youtube.com/watch?v=5ei6vTFfdAY
(Not my vid!!)

As I said in Low Elo you're playing with 9 others who are apes. Some could be good but most of them are from the primate family. What I learned to climb faster is to take everything for yourself if you know how to not int. For example if you take rift, take all the turret plating gold for yourself. See a bounty? Try to take it before your 0/9 Ezreal does. Some free farm after a gank? TAX.
You should also learn to not take every fight your team takes. In low elo everybody is just fighting constantly, it's better to farm than take a fight where you might get one kill and give away your 700g bounty. Just farm up, take the gold lead, steamroll their botlane and farm. Only gank if you are sure you can get the kill.

!!!THIS IS NOT GOOD ADVICE FOR HIGHER ELOS!!!