Building a player is easy, but building the perfect player takes a long time to master.
It does of course rely a lot on the DNAs you have available to build your player, but let us assume you got plenty to pick from in the guide below.
Here are some tips:
You probably noted each DNA strand gives a boost to three of the 8 attributes, BUT what you might not have noticed is that if you add 8 of the same DNA strands into a player, the first DNA you fill in will boost those three skills more than the second, and the second more than the third and so on.
Basically this means that the value a DNA adds to the attribute depends on how MANY DNAs which already have boosted that given attribute.
So try to spread out the trademark attributes of your DNAs to make a player who is not just focused on e.g. having all 8 DNAs with finishing in them.
Remember that the 4 physical and mental skills are very important to get a good player who can perform on the pitch. E.g. is Resilience KEY to both having a player who can perform for a full match but also who can avoid malfunction every time your opponent uses on-pitch violence against you.
Now that you know this, try again and go to the build chamber. Put in some DNAs and before build try to replace them with others to see the effect.