Exceptional Attribute is allowed in Missions. There is absolutely no reason to not play a full magician, even as a beginner (Except of course RP-reasons). The rules for spellcasting are pretty straight forward. You don't have to use all abilities like astrally percieving and projection just because you have them. And I don't think they are That complicated. I would not recommend decker if not well prepared, but mages are easier than deckers.
Hard part is knowing that some skills/spells/stuff really sucks (like banishing) or have large drawbacks. To get rid of a spirit, it's far better to have your own spirit fight it. Maybe cast a combat spell like stunbolt/flamethrower. Direct combat spells are really weak (IMO) but works on the astral. Indirect combat single target spells are only good if you have lots of dice (12-16), or they will dodge the spell. Area spells are a bit clunky because they have a too big area covered and can bscatter like grenades (risk damaging oneself and friends).