The people who tell you to "play normals or play against bots" are tilted because they can't accept that a concept called "new players" exist. Ignore them completely and just keep playing whatever gamemode you want to play.

• If you're really looking to improve, solely play Ranked Solo/Duo. Play other gamemodes if...
  • ... you want to experiment with new champions / new builds before playing it in ranked.
  • ... you want to play with more that 1 friend.
  • ... you want to play with a friend whose rank is significantly lower or higher.

Playing ranked makes it so that you are playing against other people who are actually trying as well. This can help you improve faster as you are getting accustomed to a competitive environment. Here's a few tips that can help you with your climb:

• I would recommend playing either Top, Mid, or ADC when you start playing. Jungling requires way too much fundamental understanding of the game to properly play, especially for someone just starting out in the game. Support doesn't offer the key fundamentals (most notably, the ability to CS) that is needed to play the game.
• Speaking about CS, the NUMBER ONE tip I can give you is to solely focus your time on improving your CS. CS is VERY underrated in Iron to Bronze ELO. It is arguably THE most important aspect of winning games in League, especially in this ELO. *