For a start, there is one thing you need to know:
Your pick does not matter to your skill. An "op" or easy to handle champ might get you slightly better results if you're lucky but that will not make you a better player at all.
Though no doubt some champs help newer players in learning or are a bit easier to handle for a start - the whole LoL match can be hard enaugh to play without having to handle the vectors or Viktor's E or the "7 skills kit" of Lulu while building 4 items with active abilities.
I'll try to give a few examples here:
Top: For instance Renekton or Garen. Their kits are not that difficult to understand and handle, they are tanky lane bullies with no mana or energy who can probably handle some 1v2 situations if they're ahead and neither of them is so immobile that one wrong step will necessarily kill you.
If you go by the meta and pick teleport, an (ignite) kill pre4/5 will not hurt you badly in top lane either.
Jungle: Some examples are Vi, (Master Yi) or Warwick. All of them are pretty mobile and have decent jungle clear. All of them scale acceptably with farm, you're not forced to have huge map pressure. Mistakes won't hurt nearly as badly there as on an early snowballer like Shaco. Vi and Warwick also have got kind of "no-brainer" ults towards the end of laning phase and you won't be messing up too hard on them if you just gank whenever you've got an ult to blow. Vi and Warwick can of course be quite decent on a 1vs1 against some opponent jungler, they're no scared little runaways in most matchups and they are quite sustained through shields/heals and tanky stats while they can carry pretty well when they're ahead. Especially Vi is an allrounder.
(Bot)ADC: Ezreal or Caitlyn should do. To my mind all adcs are rather similar to be honest. But you may want to go for guys that have good range and/or good repositioning tools like these two. A scaling immobile Kog'Maw will be much harder for a start and a Draven will force you to conentrate on axes additionally to playing in your lane. ADCs are still squishy per defitionem, might not be your favourite role. You will want Heal/Barrier and Flash, unless you really know what you are doing I cannot advise you to pick up Cleanse or Ghost.
(Bot)Support: Leona is a nice support to learn the role. She is really easy to play for a supp due to her kit so you can concentrate on the one important question: when to fight, engage, extend trades and when to play passively.
Taric should be a good pick too as he too is tanky while offering extra sustain to the adc and not relying on skillshots as much. Same goes for our friendly cow, Alistar.
Mid: Morgana has been a safe and strong pick here ever since she was released. Incredibly high potential there but she is also decent if not played so well as she is really safe with her 20% free spellvamp, tough hard-CCs and CC-immunity. She's more tanky than most mids.
Ahri is pretty big at the moment, too and she lost most of her complexity on the way there. Probably a good choice to train (fast) skillshots with some easy damage from her W on top and 3 jumps on a fight plus huge movement speed buffs. Let's be honest, it doesn't get much easier, even on Ryze.
What you need to understand and train are the "mechanics" of the game.
Anyone who has decent mechanics will go at least to Gold league sooner or later.
No matter if they play "op Vi" or 44% winrate Syndra as their favourite.
That's a promise, you can't even avoid it.
This being said, anyone in bronze or silver and parts of gold (or who usually goes 2/16, no offense meant) is very likely to lack important mechanics (or else to be so inactive he does not climb from ten rankeds a season only).
This isn't just csing.
You will find some people in mid elo who get their 86+ cs in 10 minutes if they're doing well and go for 220 cs in 20 and they're still there after 500 matches because they lack some other basic mechanics.
Maybe they have no idea on how to trade. Maybe they do not know their objectives.
Maybe they have no map awareness. Or maybe they are clueless on what to do after early game or refuse to take towers pre20 because they want to outfarm their opponent lane nomatterwhat.
And some players will carry tons of matches with creepscores that look horrible, (especially on assassins).
Csing means a person can rightclick minions. It is very important as it defines your steady gold income - but as much do trades, wave control etc.
Awesome csing does not mean they know their mechanics perfectly.
If you learn about mechanics and train those, you are likely to become much better.
A quite nice introduction is the league craft video to basic mechanics on youtube:
https://www.youtube.com/watch?v=6ywhB-2h2AE
The guy producing these videos has a quite acceptable amount of analytical game knowledge. He does not go in-depth there but he certainly explains some basic strategies there and passes on some good bits of knowledge.
I can only heavily advise you to take a look into those videos if you haven't yet or to watch them once more if you have.
Yet to come, the simplest, most obvious bits of advice:
It sounds like you are dying unnecessarily often.
- Don't get greedy. He'll kill you if you touch that creep? -> Don't touch it then.
- Ask for help. A jungler or a mid laner might help you out with some roaming.
- Don't fight them under their turrets if you're not certain you'll win the trade well. If it's a 100% chance they'll get a kill and your chance on getting the kill is 50%.. that can't be worth trying.
- Don't fight in the middle of your opponent's creeps! They're so so often underestimated. Minions are damn strong and if you are extended while hitting your opponent with a basic attack, the creeps will start hitting you.
- If you are low, backport safely. It's better to lose time or even the turret than to get killed under your turret or in some bush because you didn't want to walk there and lose your turret nevertheless plus more time plus a gold advantage. If you're not sure they won't get you where you are standing, walk to a safe spot before backporting. If one or the hits of the opponent will kill you, don't stay in lane for creeps or a bad gank - that easily gets too greedy.
- Try not to overextend too much. If you are often dying to roams, you are playing too far away from your safe zone which will usually be your tower. If you're hugging the opponents tower in your lane, anyone coming through the river can pick you up as a freekill. Wards are also extremely valuable if you watch the map a little.
And one more helpful general tip:
Check your settings.
Don't play with your HUD at standard size. You want to see what's going on rater than giant icons of your Q, W, E and Ult, right?
Maybe smartcast works better for you than the casual clicking?
Find out what lets you play best.