It is really a question of playstyle and perception. If you focus on just one skill, you will start getting good at those specific tasks sooner, but will struggle as soon as a new challenge arises. If you generalize - you will struggle with most tasks at first, but will likely experience a huge boost once all (or most) of your stats get better at the same time. It is really up to you.
As for the Trial. It is more about knowing what to do and understanding your strength. You can steamroll the Trial if you train correctly. But with perfect understanding of the Trial's mechanics and some luck, you can get second place even with base stats.