Enesem, I think you are looking for a very specific answer that you're not going to get.
You're not going to become a crusher by playing at any one level. The underlying goal of starting at the bottom and working up is to slowly but surely build a skill set. Maybe you won't be using advanced plays much at the lower levels, but the idea is to put in enough volume to not only prove profitability but to hammer certain basic skills into your mind so that they become second nature. You're also learning to recognize and exploit a few common player types. When you move up to the next level, you'll be exposed to new player types and have to acquire/learn new skills to win. And the process repeats with every level. Think of it like a game of basketball. Anyone can learn to dribble in a short period of time, but dribbling is borderline instinct for the pros. They've done it so many times that they're not even thinking about it in-game and can focus on other things.
As for the question about when to move up, there is no definitive answer. If you are beating a level only very marginally, you may want to stay and focus on cleaning up some flaws in your game. If you are constantly getting frustrated against bad players, you should probably avoid moving up under the illusion that you'll somehow succeed against better players. Moving up too quickly can maybe "leave some skills behind," and you'll eventually wonder why you've plateaued.
Also, nobody said you have to play strictly at one level then move up and play only that higher level. You can practice shot taking the higher level every once in awhile. It will give you a taste of what is to come, ease you into the new environment, give you an idea of what parts of your game to work on, and even give you a fresh perspective on your current level.
