Firstly, ignore people who talk like that. They're idiots. Take it from someone who gets mad at the game but chooses not to take it out on people wo aren't responsible for it.
Second, try to find some friends and play with them. In bot matches at first, if you're more comfortable that way, but if you can find some friendly people with more Normals under their belt to guide you a bit in PvP, all the better.
The most basic problem here as I can understand is that you need to work on your general build and your moment-to-moment strategy. No matter who you pick, or how good you are, most matchups in League come down to a few factors:
- Which champion you're pitted against
- Which skill you take first, then which skill you max first
- Your build order, and when you back to fill it out
- Your gameplay fundamentals
Four is the easiest to start with; it'll be things like how to last hit, when to push and where, and general rules about when to dragon, and so on. On a more advanced level, it'll be things like counterpicking enemy champions, watching enemy behavior in lane for signs of a planned all-in, or a neary jungler with an imminent gank in mind. The rest, unfortunately, have to be learned, and can change from game to game like you wouldn't believe.
There's a few solid general starting tips though. Don't always push right to the enemy tower and walk past river, especially without vision. It leaves you defenseless to ganks. Never, ever, ever underestimate the value of warding. Vision control is almost a number one priority in this game, and the factor that, in my opinion, separates the best teams from the worst. Or even the second best. And lastly, it's not always about the kills. A kill secured is great and important, and a death is bad, and should be avoided. But the game is about destroying the enemy Nexus. And it doesn't matter if your team wipes the board with the enemy team all game, it only takes one late game teamfight or baron throw to start those fourty second death-timers and spell the end of the game.
As a rule of thumb, watch people on YouTube playing your champion. Try to find someone who walks you through their gameplay choices and logic, as well--it'll help your mindset.
And always follow the general guideline of objective importance:
- Enemy Nexus (obviously)
- Enemy inhibitors
- Enemy turrets
- Baron
- Dragon
Baron and dragon are solid victories for your team, sure, and a loss can be disastrous there. But too many people overestimate their importance for one simple reason, and that's that turrets are permanently destroyed. Inhibitors are worth more for the lane pressure, and often one inhib fallen can mean that, with the right teamfighting and map control, the super minions themselves come in to the base in time to retake it for you. But towers fall and they're gone, and every tower that drops on your enemy's side of the map creates more safe area for you and your team, and gives you more control of their jungle.
Lastly, a few more general tips for any champion.
ALWAYS buy wards, no matter what. You won't need as many as your support, or your jungler, or even your midlaner (unless you are one of those) but everyone on the team should buy wards throughout most parts of the game. Wards give you and your team vision, and this is invaluable, almost priceless for teamplay. Vision over the entire enemy team gives you strategic safety, so you can plan for their positions and how long it'll take them to group . Vision over dragon or baron, or even the enemy buff camps, can reveal their timetables and potentially where the enemy jungler is. Vision over bushes, especially the commonly accepted best places to ward, can spoil enemy ganks, help you catch the AP or AD carry out of position, and can even free up one of your team to split push. It can't be understated, vision is vital.
Mobafire and a few other websites are solid places for guides; in general, you can even Google 'irelia guide' or 'irelia build' and find a wealth of articles and even videos on how to build that champion, including skill order and purchase order, and some people will even give you general champion tips, special tricks or widely known moves/combos, or even nice item synergies. Some even go so far as to plot out lane matchups for you, so you know, even if inexperienced, who might give you trouble in lane and, more importantly, why they're troublesome. This can help you counter-counter them, if they're as inexperienced as you and don't know how to take care of the weaknesses you've been reading up on. But this is second to my main tip here, which is that no one build order will always be viable, not for any champion. There will always be some variation in what you buy and when, which takes being able to read a game, AKA practice. There's always recommended paths, though, but for the most part a lot of it falls to judgment.
I know it's a lot to take in, but there's plenty more out there if you look. If you have any specific questions, ask and I'll do my best to reply. And feel free to add me, if you want, and I'll play with you sometime. There's no telling if I'll be any good though. =P