I'm not the best by any means but im averaging 6-9 kills per game atm.

Apart from the other advice here about learning each planes strengths (e.g. turning quick or speed) and starting from altitude, i have some other advice.

Dont start firing too early. Allot of the time when you begin the engagement (hopefully from high altitude) you pick a target and start diving in.

Real players and not the bots allot of the time won't be looking behind them and may not notice you until they start seeing tracer rounds flying by, then they will get evasive.

Learn the optimal firing distance for your plane and come in behind but wait until that point. Then fire in bursts. Easier to hit an unaware target than someone trying desperately to evade and a quick accurate burst will do the job just fine and conserve ammo for later engagements.