I think (at least in the US) a radical increase of affordable housing, guaranteed food (you'd be amazed how much food is wasted every year in the name of profit here, it's fucking ridiculous) and free health care (having thousands to weather a medical emergency is asinine) would be a strong base to build a UBI off of. The bootstrappers, lickers, and "that's communism and that's bad" people would disagree but for the purposes of this argument I think this is the best way forward if UBI were introduced. A guarantee for medical services and a full stomach, along with a fighting chance to have a roof over your head without having to hold three jobs to do it.

(I think we should have the above anyways as the system clearly isn't working as it stands)