Dianas jungle path is just taking her buff then going for Raptors/Gromp, she paths like most other junglers, taking everything except Krugs then looking for ganks. Her basic clear combos are to Q from afar then E to them then AA, W, AA, AA. She can clear camps really well with this combo and AA any monsters still alive.

Ganking with Diana is easy as she has a lot of mobility, similer to her jungle clear, you Q then E to get in range and instantly pop of your W, this is so that the shield can get up quicker. Then you can either keep AA or leave as you do a lot of damage with 3 abilities.

Diana mid has pretty good wave clear, you aim the tip of your Q to a large group of minions and use W as it does good AOE damage.

Diana doesn't really have a lot of combos, most of them are a mixture:
Q, E, W, AA, AA, AA
To engage over further away:
R, Flash, Q, W, AA, E, AA, E, AA
To do a lot of damage in a short moment or to mop up a fight:
W, E, R, Q, AA
In teamfights to get to the backline:
W, AA, R, AA, E the backline while you throw a Q, AA to activate the passive
Q, E, R, Flash to the backline, W, AA, AA, E, AA