pre 6-stars, where to spend Skillpoints?

where to spend skillpoints when your players are 5 stars and only a few skillpoints away from 6 stars? i am lvl 3 and i've never owned a 6-starplayer. but i've bought many 5 stars this season and i've read that 5* train significant better than 6*. so i am thinking about these options:

-spend points into SA

-spend points into another Position

-save points

-spend points for the next star

i got young expensive talents (18 / 19 years old and realy realy expensive 5,8M), young moderate players (18-20 between 3,2 and 4,5M) and some bad players or realy old players. and all of them are 5 Stars and reach nearly the 6th one.

so. which option is the best one?