As someone who just reached level 30 and finished my first ten ranked games, I would say that team builder made the game incredibly easier for me to get into because I can mechanically master one champion in one position at a time over and over again. Not to mention that there are features in team builder that allow you easier access to simply be picky on who your teammates are and choose to queue into another game with a new set of players rather than having to watch people in normal blind or normal draft pick choose those champions and being unable to effectively dodge without incurring a time penalty.
I rescind this comment. Create two accounts. One which you only play to win on and another one where you will dedicate to trying out new/different champs and rune pages. It will take awhile but having a regular account and a smurf account with two separate purposes will be more accessible to you down the road. If you try out too many champs (and lose) then you will tank your normal MMR and end up with ridiculous players who will run ADC Thresh resulting in your normals to continue getting worse. This makes it utterly impossible for you to prepare for ranked since the discrepancy will be incredibly large.
I rescind this comment. Create two accounts. One which you only play to win on and another one where you will dedicate to trying out new/different champs and rune pages. It will take awhile but having a regular account and a smurf account with two separate purposes will be more accessible to you down the road. If you try out too many champs (and lose) then you will tank your normal MMR and end up with ridiculous players who will run ADC Thresh resulting in your normals to continue getting worse. This makes it utterly impossible for you to prepare for ranked since the discrepancy will be incredibly large.