I used to be a trumpet player until I switched to bass trombone (it fit my larger lips better). I played both for about 4 years each. I have my own trumpet, but was borrowing a trombone from my high school, and when I graduated playing no longer fit into my schedule, plus I didn't have an instrument (I suck on trumpet now), so I haven't played since then. Congratulations on starting on an instrument; practicing and playing will only get more fun the better you get!
From my experience, most mutes aren't really to make the trumpet softer, but to change the characteristics of its sound. For example, a piece of music may call for a mute, but still require you to play loud; muted doesn't necessarily mean softer, as strange as that sounds. Plus, I've noticed that when I tried practicing with a mute solely for keeping the volume down, my quality of my playing would be quite a bit worse when I took the mute away because I wouldn't use the right amount of air when playing with the mute.
My suggestion for night practicing would be to just try playing softly with as good of a sound you can produce, as that will really help your breath control and tone quality. Playing softly with good sound is something that many brass players have trouble with, so if you set aside time to do just that you will really get a leg up.
That said, there are practice mutes specifically for practicing at low volumes, such as this one:
http://wwbw.com/Spivak-Whispa-Mute-i77150.music. There's also the Yamaha Silent Brass system here
http://wwbw.com/Yamaha-Silent-Brass-...m-i32348.music that uses the mute as a mic and feeds the sound to earbuds. The Silent Brass system might be overkill, though. If the practice mute is designed well, it should simply make your sound softer without changing it as straight, harmon, bucket, etc. mutes do, and should serve your purposes well.
For accessories and supplies, Woodwind Brasswind
http://wwbw.com is a reputable site that sells most everything you would need. I won't even get into how nuts you could get with trying mutes, mouthpieces, cases, stands, cleaning supplies, and even other types of trumpets; check them out!
Good luck with your playing; I hope you find playing the trumpet enjoyable!
Edit: I'm not familiar with that DVD, so I can't say if it's worth it or not, but most professional trumpet teachers teach out of the Arban's Method book here:
http://wwbw.com/Carl-Fischer-Arbans-...-i140957.music. It has exercises and pieces for all the way from beginning to highly advanced players, and is good for chop-building.