I'm taking a new approach with this game. Since I've been playing less Puzzles and Dragons lately I've begun just rolling whenever I have the orbs to roll. Since I am F2P hoarding tons of stones and rolling to not get anything I want is just an awful feeling I get probably 90% of the time.Rolling whenever has actually made the game a lot more fun for me after years of hoarding. After a couple of really bad runs with this game I am going to start doing the same thing. When I hit 20 I will just roll on whatever banner I like most no matter the colors. At least with the inheritance units can all be useful.
Pretty much how I roll, too. I saved up once and found that it didn't really make it any more/less enjoyable, so I just go as soon as I hit 20 orbs.
Though it also helps that I've been extremely lucky and pull 5* banner units within the first or second set.