honestly depends on what kind of role you're looking for besides a magic class. PK? PvE? Support? DD? ( CC? )
but since your question is 'magic' then i'll just go on a gut whim. wizard or mystic. regardless of which you pick, you'll need at least a little time to farm for decent R8 gear. wizard might be more costly and mystic a little more cheaper, considering they're not too hard to gear up for small PK or PvE. ( not saying they're easy to gear if you actually main one. )