My recommendation would be to steer clear of the plain black ties with the white shirt (makes you look like a piper) If the white shirt is all you have at this stage the try a club/old school tie/regimental style tie.

As for a belt, please do not wear a belt under 2" wide, it's better to go without one that with one that is too skinny.

In relation to your sporran, when funds allow I would suggest a leather one for work as the fur one will quicky become dirty.

Just remember, that you don't have to match every bit of your clothing, colourwise, when wearing the kilt. If you have other colour business shirts try those with the kilt with other ties. See how they look