Hardware essentials:
1) tracking software & camera with infrared clips or neuralnet. Cannot be played without!
Search opentrack. Solution with PS3eye and shipping cost around $40. Might take about 5-10% of CPU processing power. This is an entry to the aviasim world. Any camera with lens modification would work to some degree. Neuralnet trackers are said to be work in daylight lightning without IR clips, although IR is more precise.
2) joystick. Can't be played without. Need something expensive like VKB EVO or Virpil or Warthog. Cost me $100 for cheapest outdated but new VKB, expect $200-$400 minimum for really good bearings. Cheap mass market is bad, do not waste money. Almost all expensive sticks have twisting handle to control yaw.
3) rudder pedals are better than twist. Precise yaw control for aiming, for long flights without trim and coordinated turns to avoid losing speed. Are needed past an entry period, but you can play without them. $250-$450 minimum.
Where does people play?:
http://il2.com.ru/en/links.php Copy link to in game connector, it will save. If it doesn't connect you might need to force java to accept ipv4 instead of ipv6 on Linux.
export JAVA_OPTS="$JAVA_OPTS -Djava.net.preferIPv4Stack=true -Djava.net.preferIPv4Addresses=true"
Software:
1) Patch to the latest version.
2) Il-2 compare. It is outdated but gives minimum information to compare aircrafts's speed, climbrate and turn performance.
3) avoid mods for now, everyone plays without them in multiplayer.
4) setting conf.ini is another story. Just mention that IRtracking, blood, swagsticka and joystick polling rate are needed to be edited manually to change.
5) graphics: best performance is achieved on best -1 setting. I.e never choose the best, but choose one step below. Best setting might lag and distort colour. You will never see historic gray-green of Luftwaffe with the best. Not realistic!
Flying:
And finally the most important is the manual for flying. Bad pilots change altitude using yoke but good pilots are using throttle. Read why there:
https://www.av8n.com/how/
But if you have no knowledge about airplanes start here:
https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak All in-game information on "battle climb in one turn or chandelle" is given using FAA definition of chandelle. You should make it on any Soviet\German aircraft assuming 30* roll without pulling yoke on 90% throttle, 90% (or auto) propeller coarsing with default pitch trim.
In-between game sessions I recommend you to learn to fly in simulators like FlightGear. It is open source and free and there are enough content to learn how to fly basic instrumental flights, which will improve your IL-2 performance. You will be more disciplined and learn to control your instruments. Just read manual and use c172p, it's very easy.
Aiming:
First learn to fly, then learn to shoot. Simply put to see where your bullets will go fly P51-D20 and turn on aiming calculator (keybind needed). As you might see all bullets in 90% of time in maneuvering will drop on the outer rim of your circle. There are tons of guides how to aim and even measure distance using any WW2 collimator gunsight.