im new to this game but I got two of my players from 5 star to 6 star and 6 star to 7 star
but if you go to "personal trainer" it will tell you that if you want to get him up by 1 quality, he will need 8 cones each quality.
your player is at 19 quality which would need 1 more quality (8 cones) to get him to 4 star and you need 6 more quality to get him to scout star (6 stars) which will cost you like 88 cones in personal trainer but thats just an estimate
ps. go on your players card and click personal trainer to see how many cones you need