TL;DR: PCs discovered magical powers by accident, should further practice increase control or power?
Magic is often something that either exists or doesn't, but I find it much more intriguing to have it be something very mystical and hidden in my settings. I am therefor faced with the challenge of presenting magic as a slow discovery without any set bounds or rules.
Half-way through a recent campaign, my players have just discovered that some of them have the ability to affect things with their own mind, and form some basic "spells" (telekinesis, aura reading & sense life). All of this I have presented to them as a series of "accidents" while preforming other tasks. E.g. PC number one tried to get to a dagger while tied to a chair and after enough straining, the item moved the last five or so inches by it self.
Should the accidental discovery of abilities be followed by players working for control over these things or to increase the power of these "spells"?