Training magic to level 99 is fairly easy in SoulSplit3.
To start go to the Edgeville General Store and buy runes and supplies.
If your combat level is high enough you should go to the Slayer Tower and make your way up to the levels where you can safely train magic. Otherwise, fight Rock Crabs and Yaks to 99 Magic (That's what I did) with double XP from Voting it doesn't take much time at all.
If you have some gold, buy barrage runes to train even faster when you start to get to a higher Magic level, if you talk to to Zeke in the Edgeville General Store he will ask if you want to buy 1,000 barrage runes, also North of the Edgeville Bank you can switch your Spells to Lunar, therefore enabling barrage attacks.