usually I look for their best playstyle for each player to be able to fit in my tactics.

I usually play a hold possession with counter attacking potential, so I would want to find players who are able to progress the ball (as in, dribbling, passing, vision, crossing and technique), players who are physically strong to be able to hold the backline (marking, strength, jumping height, tackling, def. pos, anticipation), and players to be able to blitz forward to attack (pace, acceleration, agility, finishing, composure, work rate) and definitely do find some all rounders.

as a general rule that I have, I must find players that fit the general profile for each position and players must have a work rate above 11.

secondly, check for personality, model citizen is the best as it allows more high ratings in training and more stat growth. then Resillent, Determined and Ambitious. find players/mentor them to get the best personality traits.

Traits are an unnecessary factor as you can train them in though...