There's many components to off ice training. The first part is to find someone who is very familiar with ice athletes and customizes a program.
Off ice is for:
Cardio fitness, although nothing trains skating a long program other than skating long programs, but spin classes seem to be the best substitution
Balanced strength training/injury prevention with weights or machines since skating itself creates muscle imbalances, quads vs hamstrings for example
Flexibility, and there's muscle training, eg abs and then there is leg flexibility of which there are all sorts of options, pilates, yoga etc
Rotation and twitch - which can be separate from off ice jumping
Power - Plyometrics
Artistry - ballet, modern dance, jazz, etc
Mental Training
So an elite skater will do two ice sessions a day, sometimes three and then spend twice that much time in the gym. An hour of cardio, hour of pilates, hour of ballet and hour of rotation/jumping, which could also be warm up before ice sessions and then add another hour of off ice program runthrough visualization and sports pyschology, there's a nine hour training day. Not everyone does everything. They'll do different things every day, eg ballet might just be twice a week.