Diana is strong AP champion played jg/mid/top lane. She is strong in every stage in the game. She is not hard to learn but very rewarding.
Jg: You can start blue or red depends on where you want to gang. Your clear is good on both sides. Once you do this you can start ganging. Combo that you can learn is E than Q on the target so you can take the cooldown reset, then you can proke your conqueror and win the trade. Once you hit lvl 6 you can go bot or mid,as you can one-shot the squishy champions! Late game you do a lot of dmg of structures with your passive, as well as a ton of dmg on champs!
Mid&Top: First 2 levels you are not strong and get poked, so just stay back and farm with Q. Lvl 3 you can look for trades, as you can proke your electrocute(on top look for extended trades, like more Q-E combos) with the combo E-Q-W-AA(-E).