To me one of the major differences between high elo and low elo is tactical play, you can be the best mechanical player and be stuck in low elo forever, mainly because this game mechanics are very simple, this is considered an MOBARTS after all so tactics are a lot more important than mechanics, specially in Dominion.
With that being said, the main difference I find is, in high elo games, usually things go like this:
Fight for Wind Mill, did you win Wind Mill ?
If yes: Jungle control > defend your mid and watch out for bot ganks.
If No: Jungle control > Try and take their mid or gank bot while making sure your mid is safe.
In low elo it usually goes like this:
Fight for Wind Mill, did you win Wind Mill ?
If yes: Good, camp it all day, make sure it's in plain sight as well so the enemy knows you mean business.
If no: Keep farming minions all day trying to push wind mill, it doesn't matter if there's a Malphite there and Heimer turrets, the enemy should fear your tower dives even after they fail for 10 minutes.
In basic terms. gank bot a lot, don't bang your head against the wall to try and get wind mill all game, look for opportunities to force jungle fights where you are at an advantage ( catching someone out of position while walking back) go and 2-3 cap their mid to force a fight, basically do everything in your power to not let them sit at wind mill all day, communication is key so make sure you tell your team mates to do this, most of the times I find people will cooperate and be open to suggestions, if that fails, gank bot, pick strong jungle champions like Evelynn, Kassadin, Talon to get to high elo, if you are a good player you will stay at high elo regardless as it's mostly about tactics so as long as you read guides, spectate tournaments/streams you will understand those quickly.
The best advice I can give you is don't listen to high elo people in these forums telling you not to play OP champs, if you really want to get out of low elo this is the easiest way. I played a lot of Jax bot and Kassadin to get high, I'm at a point now where I'm basically top EUW and I can still win playing AP Trist or Ashe, Champion picks are VERY important at low elo as no one really knows tactics and most of it comes down to wind mill team fights.
Also, read Saurons super duper guide, not the champion parts, the tactics part as these are super useful and will teach you a lot you would never learn until you get to high elo.
Oh and the most important thing, don't get frustrated in solo que, soloque is not half as bad as people make it sound like, I met most of my favourite players in solo que, usually people are open to suggestions, I find only 1% of soloque is toxic in Dominion and I honestly can only name 2 players from the top of my head that are toxic, and this has been from playing Dominion for at least a year, keep calm, communicate with your team, don't feel demoralised if their team seems a lot stronger than yours, I just 5 capped a kassadin/talon/wukong team with Fiddles/Ashe and Renekton (390-0), where there's will there's always a way, once you start seeing 2-3 revives in your team you have arrived at a good elo, now your biggest problem isn't Kassadin/Jayce/Teemo players, it's 4 man premades who have been playing together for ages and are super organized and win tournaments, these players will basically make your elo climb a living hell, you will get stomped by them but you will learn a lot from them (Tactics), even if they taunt you just ignore them and instead choose to see how they outplayed your team and don't think (Omfg!!my team sucks, bg !!1) , get through this, you probably wont win against these premades but luckily you won't see them very often as it's technically a match making problem, if you play during prime times you probably won't even see them as their elo is a lot higher then yours, once you start seeing 4-5 revives in your team consistently, congratulations, you have arrived at "elo heaven", feel free to pick whatever you feel like and don't give a flying fck, I've mained AD Carries through the Teemo BFT crazyness because that's just how I roll, follow tips, don't rage at your team and read Sauron guides, play strong champions and strong bot laners, I give you 4-6 weeks and you will be out of low-mid elo if you're good enough.