Well, since you asked the question in an open forum, in my opinion, the chances are very small.
They are very small even for the best of the group because typically all these players have been exposed to college and professional scouting to the point where a solid understanding of their ability is already known.
Usually a player knows where they stand when they enter the independent leagues. Every once in a great while, one of major league caliber is overlooked and finds his path to MLB through an Indy league.
The vast majority of them just want to continue playing the game and were good enough to sign an independent pro contract. And they live from paycheck to paycheck. Life and all that goes with it usually forces them to enter the workplace so they can raise their standard of living. Now this is something I would expect everyone in this position realizes before they go to a tryout.
Scouting is so widespread nowadays that very few unknowns show up at an open tryout and impress anybody. No matter what the level. Bob Feller’s don’t just walk off the farm anymore.
But hey, I salute your aspirations. You could be the next Mario Rivera…after all I’ve never seen you throw! Good luck.