Which cards do you make into Steel Cards?

I have been making my Queens into steel cards, since the +mult Queen Joker is categorized as “common.” So in the hopes I get that Joker. The King joker is so rare I don’t invest in it.

My other train of thought is to make 2’a and 3’s my Steel cards because I usually won’t use such low scoring cards anyways.

Which cards do you usually make your steel cards? Is there a best route to go?