The aeroplane itself is not so important as is how competent you are as a pilot and thinker of suitable tactics. So I would suggest that before you go and get all aggressive
choose the aeroplane that you like best and spend quite a LOT of time just flying it and getting to know what it can and can't do well.
And use a stop watch! Time yourself making 180 degree turns - then practice until you can better that initial turn rate. Then do the same at various heights - because whatever aeroplane your flying it WILL vary in performance at height (thanks to the excellent work of the OFF FM developers). Keep a record. Same for climbing, measure time and speed until you get the best you can. Stall the aeroplane and measure how quickly you can recover (as in losing as least height as possible). Then practice until you can better that time. Do the same with spins. Yank and bank until you find the point when the aeroplane loses speed and drops out of the sky. Keep notes so you know what to watch out for and avoid.
If you want to fly online one of the very best manoeuvers to master is the "level turn", that is being able to turn any number of degrees without losing height. Very few pilots (especially online) can do this. If you master this you can outturn a Camel in a Pfalz! You'll find that you keep height and your opponent is all over the place trying to stay with you.!
Once you've mastered your aeroplane THEN your ready to take on others. "Think" about the tactics you can employ against your opponent. There's enough info around to provide a general sense of what various aeroplanes can do as in speed and turn capability.
* For example don't get into a turning fight against a Fokker Dr.1 or Camel if your in an less capable turning aeroplane like a Pfalz, Albatross, Se.5 etc.
* Use height, make a diving attack and zoom for height, or simply make one attack and dive and extend away.
* If your in a great turning aeroplane get in close and hussle, make your opponent twist and turn and burn off speed.
* Never get caught below - run away and fight again another day.
* Watch your speed - avoid being caught low and slow.
* Treat each combat as if you DO run the risk of dying. That way you won't take silly chances or fight against odds.
And most importantly practice shooting until you can hit what you aim at. The closer the better, and only fire when you absolutely sure you will hit.
Your there to win.