if you are upgrading from the builder, I would try to prioritize items that are impossible or difficult/expensive to change or add after construction.
I'm very happy that I splurged on electrical and lighting. I laid out my floor plan with my furniture and managed to locate extra electrical outlets and fixtures. Because the ceilings are exposed concrete some of these electrical boxes had to be cast-in-place into the floor slab during construction, something that's impossible to do later. I also added lots of pot lights and high quality track lighting which makes any interior look great -- most condo interiors do not provide have enough lighting to begin with.
Having gas cooking in the kitchen and a natural gas line on the balconies is also a great feature to have especially if you love to cook, however it is a very rare feature in condos and only a few developers do this.
Surprisingly, there are a few developers that still use popcorn/stippled ceilings. This is a real pain to remove later so if you can upgrade to smooth ceilings, it will be very worthwhile.
All of these upgrades are also dependant on your developer, as many developers will not entertain any changes/substitutions or customizations as it involves a lot more coordination, take longer to build, and a greater chance of screwing up, as units are built cookie-cutter style.