Originally Posted by Sereg Anfaug
I think the problem is your extremely casual attitude toward the game. Two to three games a week is not going to provide consistent enough practice to learn, retain experience, and improve - as you have noticed.
The problem isn't that you're new - its that your skill level isn't at the point that's expected for someone of your summoner level, because you don't play enough to increase it at the same rate as your peers.
I highly recommend you increase the time you spend on the game. If you're unwilling or unable to do that, but still enjoy the game enough to keep playing, you may want to consider switching to AI, instead of PvP, since your opponents don't learn at all, and won't have the edge over you that PvP opponents will. AI does teach you bad habits, but that won't become a concern unless you actually do increase the frequency of your play enough to return to PvP, and if you are playing that much, you'll start to catch up.
I don't think level matters too much, though. Lots of skilled players have Smurf accounts, and lots of people go all the way to 30 against bots, and then find the curve going back to PvP all the steeper.
I was intimidated of PvP for a long time myself, so I have very few PvP matches for someone of my level, but I actually found low-level PvP matches were often a lot more forgiving than playing Intermediate bots, because while bots often lack creativity and flexibility, they also make fewer open mistakes and lapses of judgement.
Also while practicing more will always help you develop, practicing core skills under a mentor or in LoL University will improve one's game a great deal. Also while steady practice is important, so is healthy downtime. Very often stepping awa from the game for a few days or weeks can refresh your mind and your enthusiasm, letting you see the field from a fresh perspective. That's what I've found anyway. Again, take that with a dash of salt.