As a non-GURPS player, the idea of making a "300 point build" sounds pretty intimidating.
First, the GM would help you.
Second, there's 300 and 300. If you want an extremely versatile wise man who also dabbles with magic and can keep one swordsman at bay with mundane combat, then you'll have a large number of Advantages and a very large number of Skills and Spells. That's feasible with GURPS, but probably not entirely recommendable for a beginner.
OTOH, if you want a super who is extremely strong and who has one remarkable superpower, you probably sink 200-250 of your 300 points in just those two items. That simplifies things.