Well i personaly think you best bet is going jungle or solomid and picking a champion you enjoy playing and your willing to chunk alot of time into, a champion you enjoy and are willing to put alot of time into practicing with will always be better in my opinion.
I have been using Jax solo top and went from 1200 to 1488 in the past 2 weeks. I feel Mordekaiser / Tryndamer / Sion , Lee Sin lost his ability to carry imo. Any champion you feel is OP but not banned is your best choice.
My best advice is to play the "Flavour of the Month" champs. There's a reason they're popular, they're good. Don't be afraid to AP Sion or Kennen, they win games!
Kennen is a fantastic pick, always in my opinion. Even if you aren't doing well, it doesn't change the fact that your ult can stun the entire team!
Part of it is also picking champions that you feel confident and comfortable with. You don't' want to play something you don't know how to. I climbed the ladder using my most comfortable champions, and it worked.
That being said don't be afraid to practice in normals. =)
I guess I forgot to mention who I played to get myself out of "elo hell".
In season 1 I climbed out with Janna surprisingly. Supports really can contribute, just people get into this mindset that supports don't do anything, when really they can make or break games. I've carried many a bad AD carry with Janna just by keeping them alive in the lane phase and making it to mid/late game without having anyone feed.
This season I actually used Cassiopeia, although I wouldn't suggest her unless you put in some practice. Playing her helped me get to gold, but nowadays I can't play her to safe my life. =P
I have some advice, not trying to be a D**K, but I recently have had success in solo queue, after being 1100 season one and spening up until this past month between 1250-1380 for season two I am now 1534 and expect to keep going up. Well I think knowing who is flavor of the month and what champs are OP is important for solo queue. It is way more important for you to be able to play every role confidently. If u learn 3 strong mids solo queue and don't get mid you hurt yourself and you hurt your teamates. When I'm doing solo q and someone says I can only play mid, I give them that position and politley suggest them not playing ranked anymore until they can fufil every role. I didn't start to rise until I could play every role, mid is my main and I play every AP, but I didn't always get mid. So I stop playing ranked until I had 3 champs to play in every lane. I would suggest doing the same you will see a huge difference, I went from 1283 to 1534 in 3 weeks, I duo q'd for about 1/4 of those games so I still did the majority myself.