First of all, let me introduce myself.
Currently, im 60th in asia leaderboard. but the very first day i play, i suck. Just start to understand the basic after nearly 1000 game played.
So, i believe, my guide will help newcomer improve your game sense alot.

Let gets start, there is something new player need to know about this game.

-As a non target game will a slow speed projectile. I suggest you should practice with melee first. Theyre hard to miss. strong dmg output, and easier to play for beginner. In fact, if we put 3 new range champion OP ass aside, melee have a lot of powerful character which is strong and easy, bakko/raigon/ulric/thorn... you should try them first, to get used to this game mechanic.There is two arch type of melee: defensive/offensive. i usually distinguise them by the way their counter work. Defensive have shield/parry type of counter, in the otherhand, offensive usually have one time trigger counter.
My suggest for beginner is bakko/ulric/freya/raigon/ruhkan/shifu.

- Second: Decision.
The most common mistake that i, and every newbie i encounter is throw everything you have left at the opponent, with out hesitate is it really make more value than moving and left click. The most terrible mistake is use long range, high cast time when the enemy is nearby. By doing that, you miss the damage that you can deal if left click, risk the damage taken by them and give them a preparation time to dodge or counter or evade. The rule of this game is to hit more than get hit. So dont risk yourself try to do something if its not a game change decision.
Long story short, you should aim properly with your ability, try to hit them and follow a chain combo by it. when you dont have a chance to cast an ability and land it, stay readiness and dodge their ability and wait for your turn. Never waste all the ability in a short time, always keep a trump card for yourself, sometime, even a Raigon's RMB can save your life.

###IMPORTANT:
Space or leap/immaterial/iframe type ability is not something you can throw away easily, dont use it when you not sure if you can secure the kill fast. Space is the only way to evade an undodgeable ability. Like most of ultimate, area effect damage. Save it to the most necessary moment. Especially when your enemy having ultimate. If they have full energy bar. DONT use space if you cant die at that moment, save it when the ultimate sign appear above their head.
With your ultimate, in my opinion, ultimate is stronger when its not use. If you have ultimate, dont throw it away fast, wait for them to out of iframe/leap/immaterial. If you encounter someone waste those iframe ability fast, land your ultimate and gain max value. If you encounter someone know to keep it. dont use your ultimate, Fight them as they dont have iframe when they handicap themself. At the moment theyre losing and nearly die, they will use it and thats the chance for your perfectly executed ultimate.

-Third: Play style.
Most of top tier can outplay hard and engage/disengage a fight like just walking around in a garden, but i assume we dont do it here. So, i will share my style and i believe its suit the beginner.
First, dont drop near people, the ideal situation is drop to a place that you alone take all the loot. but if you cant do it, drop far away from people, get 1-3 loot orb and join the battle later when the other fighting and lower their HP bar.
Second, dont chasing people for to long, its a waste of time if someone want to get away but you dont have a good saddle. you can invest a little time, but if its not going to finish soon. leave it and save for later. improve your power is more important.
Try to farm as much as possible, at this patch, there are a lot of shop that you can buy almost everything. So farm gold and buy you good stuff. Keep keyring at the early to mid game, only throw away when you have other good legendary to replace. Its will help you alot to maximize your power.
Dont engage people have 10+ tier above you, mounted and run away, if they want you so bad, run around, alert for other people to join the fight, manipulate them to fight each other and sneaky leave the place. wait for someone die. when you run away from them with your foot, at the moment they stop chasing you. you should mount immediately, because theyre mounting right at that moment, if you keep walking, youll get caught. The very same when you chasing someone, if your gap closer ability cant touch them at that distance, mount immediately to chase after. dont waste space.
At those very last circle, let be a neutral, harass both enemy, if anyone lower their HP bar first, lets target on the other, because of the healthy one will goes for the kill and forget about their safety, in the otherhand, the lower will fight with all his have, even if the healthy take the kill, he will hurt a lot and its your time to finish the dirty job. Sometime they can perform the kill perfectly, but not often, especially with you harassing around.

-Forth: Gear selection.
In my opinion:
with legendary tier
Reaper edge>breast plate>ravager>boot>quickblade>Circlet>saddle>keyring>amulet>sheep
With non legendary, reaper edge is a must, quickblade is which, only keep epic if you dont have anything better. the other HP boost lets just keep the most %HP additional.

-Fifth: cancel ability.
Most player dont know cancel mechanic, so if you dont. Please read this.
Cancel default bind as C button. Which is pretty hard to use because of the button position and you usually miss the timing to cancel those medium cast time ability. I suggest bind its with a key easier to press, with my case, i use Lshift to cancel ability. some one have enable the interupt by moving. but its cant cancel those ability can cast while moving, and a lot of time you stop your mounting/healing/casting just for a sensitive moment.
Remember to cancel ability when you realize its will not make profit anymore, especially when enemy press their counter. in the otherhand, if you gonna counter, timing it with those last moment, dont press to fast cause enemy can cancel their shot, or switch to use a bypass counter ability instead. both waste you a counter and risk the damage.

Follow these guide, i believe you can pretty much understand more about this game, ask me anything if you want to know.
-[C!E]OlcImt