The above posters are correct. A nice (black or gray) Argyll is the way to go. Pick up the matching waistcoat, that will go a long ways towards making the jacket ensemble "dressier". Also, as stated above, avoid the tweed for your first jacket, as it is really not the right jacket for more formal events. Tweeds are nice, but less flexible.

I wanted a nice formal jacket, but not a PC. I ended up with a really nice black Argyll with Braemer cuffs with a matching waistcoat. It's perfect, all the way to black tie; but I can also wear a normal dress shirt, lose the waistcoat, and be much less formal with it.

Don't underestimate how much the sporran can affect the ensemble, a jacket will take on two very different looks with two different sporrans.