.....is there anything else that you recommend to be fixed/ upgraded/ maintained at the same time?
Depending on how often you ride it, you might check the brushes in the Alternator. When I got my '95, it had sat for quite a while and the copper slip-rings where the brushes ride/touch was tarnished to the point that it wouldn't charge well if at all.
What spare parts do you guys suggest to carry on the bike?
I guess that comes down to your personal comfort level of roadside repairs, and how much you want to pack/carry. For me I probably carry too much, which makes it a challenge for packing and weight distribution. When I'm packed for interstate cross country travel I have the tail bung and the entire right side saddle bag filled with spare parts/tools/supplies and a first aid kit. I suppose if I put it all on a scale it's near 30Lbs or so. In my right side case I carry all of my wet/cold weather gear and the cover for the bike.
So far I have been able to help other brickers more with what I have packed than what I have needed myself. I'm ok with that.