Here is some advice I can give
First is to experiment with weapons. Find what style suits you best
Snipers - High Dmg, Slow Speed, Very High Accuracy
LMG - Med/High SMG, Med Speed, Short/Med Range
Assault Rifle - Med/High Speed, Med/High Dmg, High Accuracy
SMG - Very Fast, Low Dmg, Short Range
There are some other types I have yet to unlock that im sure someone else can enlighten you all on.
Buy a premade for each type at some point. IF you plan on playing period and have a couple bucks, buy the starter pack