Masters runner here, so take it for what it is worth. My goal is a 10k. I've been doing:
Tuesday: Fartlek or Tempo
Friday: Hill repeats, 400s
As I have gained fitness, I have progressed towards:
Fartlek: 10-15 x 1min on 1min off (3 weeks), 6-8 x 3min on 2min off (2 weeks), 6-8 x 4min on 1min off (2 weeks), 4-6 mi tempo (planned for next few weeks)
Hill repeats and 400s (alternate weeks): 12 -16 ~400m hills, 10-16 x 400m with no more than 60s recovery.
At this point, my focus is on the recovery, i.e. keeping it short. As the weeks go by, I have shortened recovery by > 50%. All workouts are by effort and I'm staying off the track until January. Weekly mileage progress 35->60mi in 7 weeks thus far. I will probably top out at 70mpw (prior injury concerns). Another important thing to remember is, don't be afraid to push a workout back if you have not recovered or are on the verge of injury. Good luck!