League issued uniforms and commercially available referee kits usually do not come with a soccer referee watch.
As well as managing the overall game time, you will need a soccer referee watch to keep track of certain important events such as cautions, send-offs, game suspension, etc.
A normal watch will not have specific functions that a soccer referee watch offers such as count-up and count-down timers. While you may be able to work out the time mentally using a regular watch, a referee watch will allow you to manage and focus on the game much better.
There are many kinds of watches available for refereeing soccer at varying costs. For new and intermediate referees, one of my favorite and best soccer referees watch is the Ultrak Soccer Referee Watch.
It features a timer with a stoppage function, a countdown timer, and a secondary count-up timer – this is really useful for managing half time and added time.
The Ultrak watch also has an electro-luminescent backlit display which is great for evening matches. It also features a 1/100 second stopwatch, time of day with an auto-calendar. It is also water-resistant (hopefully!) so that it can be used rainy weather.
Another watch that I like a lot is the Champion Sports referee watch. It supports programmable count-down or count-up timing feature, a secondary timer, water-resistance up to 300 ft., a push-button back-light illumination, and a rugged watchband. The Champion Sports Referee Watch makes a great second, backup watch for a referee.
I personally use both of these watches (at the same time, one on each wrist when I referee), one to count down and the other one to count up. I highly recommend either one or both of them.