[Cycling] buying a pushy - what should i look for

I need to buy a pushbike - however I don't really know anything about mid range bicycles.

My budget is up to $1500, the terrain I've got to cover to get to work will include dirt roads and highways. The distance to work is ~15kms

What sort of thing should I look for? Are there hybrid mountain/road bikes that will handle the dirt and the tar ok? I want it to be light (I'm not that fit... yet), and I need it to be comfy -

What should I look for in a bike, and what do you recommend?

Spending over $1000 on a mountain bike is a joke these days unless you want to do mostly off road. Large shocks are unecessary. Also I wouldn't spend much over $1000 on your bike until you are serious and know what you want.

If you want comfort I suggest go with a straight handle bar. Replace the stock seat with one that suits your body

- what sort of accessories should I be considering?

Shoes
Cleated pedals (I assume these are the locking pedals I've seen on the racers?)
Repair kit: tube/pump/tools of some sort?
New seat? - what should I look for in a seat?
Semi slick tyres
Helmet: I assume that rosebank stackhats aren't too popular anymore - anyone got suggestions?
Gadgetry: Lighting (I will be doing some night riding), speedometer? anything else?
Clothing: I assume a high vis shirt or something would be the go?

Have you ridden with clipin pedals before? If you haven't I wouldn't suggest them for your first day of riding to work, especially if you're around traffic at all.

Repair kit is really up to you, all you really need are the tools to change a tube. Anything more than that and you wouldn't want to be doing it in the side the road anyway IMO.

Seat is a very individual thing. What ever you have you'll probably find it uncomfortable at first so don't immediately think it's crap. Make sure the shop spends some time with you setting up the whole bike to fit you correctly and you can then experiment from there.

Helmet largely comes down to budget but try before you buy. Again comfort is important here.

Gadgets you really only need front and rear lights. Anyting else is up to you. Don't waste money on a little AA battery front light (flasher is OK for visibility) but if you're going to ride at night look at a decent setup, halogen at least. The one I use I'd recommend but I don't think you can buy them currently as the company recently merged and is revamping the line up.

Clothing get proper nix at least. If you don't want the superhero style skin tight stuff then you can get MTB baggy versions which have the skin tight stuff built in. Again it's a comfort thing. Normal shorts can chaff and then you'll be uncomfortable for days. Do you have somewhere to shower and change at work?