Budget is simple and is usually the tightest and most evident constraint on promotional clothing. There will usually be a limit on what can be spent, and within that limit the clothing has to be effective and attractive.
Appearance can be shaped by material – cheap T-shirts do not last long, but if you are promoting a short-term event such as a weekend sale or a festival, they may be all that is required. More substantial materials will give a longer life to the garment and a more solid appearance to the clothing which reflects on the brand the promotional clothing supports. Bear in mind the climate and population in your chosen area: if there are many older residents, you are more likely to succeed with polo-shirts than T-shirts, but if there’s a large student population, jogging pants and T-shirts will be much more popular than classic clothing items.
Performance is part of the process of applying promotional clothing to the world. If you choose embroidered baseball caps, they will get much more wear in summer than winter, while knit hats will be more popular in winter than summer. Barbecue aprons are summer clothing but gloves and scarves perform best for their brand in winter. Making a wise selection gets your message out their for the maximum period of time, but other businesses will know this too, so don’t disregard the competition when planning your promotional clothing: your garments have to be attractive to get worn as well as season-appropriate.