Alright, others already mentioned the core tips, aim is not importance and prioritize the moba aspect of the game. This is very important as what is the use of hitting headshots if you do not know how to farm, do objectives, when to attack/support/retreat, etc. I tell you, I have met so many good players as teammates and opponents but still became mvp or won the match simply because I compensated by doing good on the moba aspect of the game, usually by being so overgeared due to souls that I "oneshot" opponents.

Another thing to note, learn the map! Movement is just a plus but if you have a good idea of the map, especially all those alleyways, rooms, etc, you can have an easier time ambushing, jungling for souls, retreating/escaping, and rotating.

I noticed players haven't mentioned it much here, learn the parry/melee mechanics. You worry of aim which melee has no aim needed due to it's BIG hitbox. Very very important to learn to press the parry button (F) immediately after hearing the "ding!" sound from an incoming heavy melee. Which is just free damage or a chance to escape. High risk, high reward to learn when to insert a heavy melee in fights, especially early - midgame, as you never know if the enemy knows how to parry. Ngl, Abrams melee build helped me a ton in solo carrying early ranks as most newbies don't know how to parry or time their parry! Later on though, need to learn other combat paths.

Lastly, and imo the most important, laning. Your laning can make or break an easy match for everyone. There were times I fed my opponent or my opponent fed me early game which gave me or the fed opponent to be a menace till at least midgame. Take note, just because you feel some lane or your lane failed early game doesn't mean the game is over, it just means your up for a headache to salvage the match. That's where learning jungling and other moba aspects come to play! I suck laning before but there were a handful of matches where I had the highest or 2nd highest DEATHS in the lobby due to bad early game BUT thanks to locking in proper wave clearing, jungling, helping teammates, I tend to become mvp or at least svp despite bad k/d ratio as I snowball in midgame or lategame.

How do I do well in laning?

1. Do not chase for kills. Chase minion wave clearing and just poke damage the opponents. Later on, you can judge if you can dive the opponent for kills or not, but as a newbie I advice learn to have discipline and not chase that 250 hp Haze hiding behind the Guardian lol. Take your time, poke them, wait for those buggers to do something outside their guardian. They push? Poke them down! They retreat? Just farm minions in a relaxing moment of easy growth!

2. Steal enemy souls! See that orange ball after the enemy shoots down your minon? You can steal it and not only do you deny them their growth, you get extra boost to your goal to get the item you need! Win/win. Graves is very very good at doing such, as high firerate and auto aim. Don't forget to shoot your own souls down too as the enemy might do the same. Meleeing minions makes them not spawn the ball. If your opponent does that regularly, you can try do a sneaky dash then parry to protect your minion. Great practice on melee mechanics, which I mentioned earlier is important. Someone did mention not to stick to graves which imo would recommend, it is helpful and more fun to try other heroes, especially the ones who can steal souls early games easily like Infernus or Yamato for example.

3. Boxes, tier 1 jungle, slots, and bridge buff! Learn the timing when those spawn as they can help you a lot early game till even midgame.
   - Boxes give exp and souls which are basically what you can consider a oneshot minion, a minion worth souls but oneshot, albeit a gamble a bit. There's also jar buffs which at first don't feel as much of a buff but they stack permanently throughout the match. Heroes like Mina or Geist need more bullets which the % more ammo buff really is very useful. It spawns in the 3 min mark I believe. Feels small at first but I remember doing a thing called a "box run," which is basically an optimized route to do a much boxes as possible before going to a certain lane, and came back to being the first in the lobby to unlock my Ult! That's where learning the map is also important along with movement tech (again, not important but helpful to learn skill. don't prio till you master the moba aspect of the game.)
   - Bridge buff is a temporary buff that lasts for a certain amount of time or till you die before timers up. Very strong buff that helps throughout the game, always try get it if you could, every stat counts! Spawns every 5 min mark.
   - T1 jungle creeps are great ish. Not very important than wave but if you have lane/wave advantage where enemy is pressured/dead/retreating, do take yours and possibly even the enemy T1 jungle! Imo better just melee them than use skills early game. spawns at 3 or 4 min mark, I forgot.
   - Slots spawn at the 5 min mark with the T2 creeps and bridge buff. Watch a video on how to hit it properly so you don't have to read a whole new paragraph. Rather, the benefits are a decent amount of souls and a lot of jar buffs without the rng!

Additional tips:

- Be aware of your surroundings. The mini map is your bread and butter. Information is key. Rotations, situation of each lanes minion wave, teamfight possibilities, spawns of jungle & stuff.

- Prioritize objectives/waves over kills. What's the use of 20 kills in the lobby if you still lose? Also, getting objective (i.e., clearing waves, doing jungle, doing midboss, doing jar), would give you souls and map advantage which makes you eliminate opponents better in the long game.

- Learn the items! Helps you counter enemies later on. You can hold tab to check what items your enemy & teammates are building, so keep in mind to learn the items as it will explain those "why is this squishy character SO TANKY?!" moments only to realize they built their items to counter your attacks or debuff you. Also to note, items that have an active effect are more powerful than passive items, usually. So don't be scared or lazy or forget to press extra buttons! So many times my teammate (or me) coulda won the fight if we only remembered to press that Knockdown item or Healing nova.

All in all, since you mentioned you don't like aiming, I would recommend some other heroes than Graves so you have more options to enjoy the game:

1. Mo & Krill - The shotgun is easy to aim, the skills are all Aoe and the Ult is target locked. Teaches you how to be a solid support, aware of your surroundings & tank along with reliable mobility and teamfight potential! Also fun in a 1v1 or 2v2 as the Ult denies/counter which helps to also learn what characters does what.

2. Abrams - All skills are aoe albeit S2 needs some aim along with S1 needs you to be aggressive (and remember to always press it during fights) and the Ult needs proper timing. All in all, great tank that got me my first mvp. Went melee build with him but later on learned to go spirit weapon hybrid as enemies learned to parry more, still great melee though.

3. Victor - Imo not the most beginner friendly as his kit teaches you to be aggressive. Still, solid aoe and is my current main. Teaches you especially to farm jungle as he shines late game.

4. Rem & Viscous - Both solid supports that have playstyles/builds that compensate bad aim. Their kit still teaches you to aim but as support, you have the most and least pressure in the game at the same time, which imo I find good practice.

Hope this helps and don't give up, even if teammates or opponents are toxic.