A crap shoot
A crap shoot (English) — A long shot, something that has a limited possibility of occurring. It indicates that there may be no, or little planning ahead for it.
Craps is a game involving dice thrown to gain favorable numbers to win. There are many ways to win or lose so nothing is a sure thing. If you have many options on an action then it's a crap shoot. How to invest money and with whom, and will you see a return on investment. It's a crap shoot.