ill give u some tips

Start with buying the Enfield but as soon as you can get the Famas then go up in this order

Galil
Ak-47

i tent to use the iron sights for every gun its wat ever u pref.
Perks i manly use Ghost Warlord and Hacker i have used loads ov diffrent combos and this seens to work well together as long as u have a Suppressor. and then what ever else u want. Also try and get Perks up to Pro much better hope it helps.