In the US, the top policy goals should be universal health care, more generous unemployment benefits, better-designed retraining programs, and an expanded earned income tax credit (EITC). The EITC already functions like a guaranteed basic income for low-wage workers, costs far less than a UBI, and directly encourages work. On the business side, reducing the indirect costs and payroll taxes that employers pay for hiring workers would spur job creation, also at a pittance of the cost of a UBI.
Note that economists always evaluate policies like the Universal Basic Income relative to its next best alternative. If the alternative is better, we say that the opportunity cost of the UBI is bigger than its benefits.