I know some good places to train magic and I will write
them down here.
The trapped monk of zamorak in varrock palace is a good way
to train but if remember to bring lots of runes when you train
against him I would recommend people with magic lvl 20-40
to train against him.
Port sarim jail is a real good place to train magic there is
a caged goblin called wormbrain (you must have started
the dragon slayer quest to be able to fight him) and a
black knight a mugger and a pirate I recommend people
to have 1-40 in magic lvl when they train there.
Chickens north west of lumbridge is agood place for
people with 1-15 in magic lvl to train.
The caged lesser demon in the wizards tower is a good
place to train magic lvl 40+. And if he drops things you
can get them by tele grab.