The first thing to think about when buying shoes is comfort. You should get the shoes you need rather than the shoes you want, although both would be nice!
It is not advisable to buy shoes online unless you know exactly what you want and you know they fit well.
When buying shoes it is important to think about the toes. Is the toe area wide and deep enough for you to wiggle all 5 toes freely within the shoe? If you can you are less likely to cause clawing or rubbing of the toes and the resulting corns that often accompany this.
It is also a good idea to have some sort of fastening for the shoe whether it be a lace, a buckle or a Velcro strap. The foot will be more secure in the shoe with less friction resulting in less hard skin. In less secure shoes the toes will often curl to keep the shoe on again potentially causing clawing.
As with many things it is good to buy a better quality shoe. They will have a leather or rubber sole for increased shock absorption and last a lot longer, having a knock on effect for knees, hips etc.
Finally, it is always a wise idea to get your feet re-measured occasionally. Feet do change shape and often flatten out creating a longer, wider foot.
For trainers, I really like the New Balance 880. Very comfortable, and accommodating.
For work, I would recommend a Clarks Brogue. Leather and very well made.