HI all, I actually have 18 years experience as a Commercial photographer so I can offer some good advice.
First off the home made light tent, is a nice try, if you check out this link,
http://www.bhphotovideo.com/c/shop/1...es_Blinds.html
You'll see there are many light tents already being manufactured, some for less than $50 and up. And you can use a 100 watt bulb or two or 3 for the lighting.
What makes these better than a cardboard box is the ability to light from the sides, back top etc. and you won't get any yellowish tint bouncing off the cardboard!
However these little tents are really only usefull for very flat lighting to completely show a product, smallish product, a Tshirt unless folded won't fit int thier and you don't want flat lighting for a Tshirt anyway.
Basic photography when it comes to using a tent for example is the further away the light the darker it is, obviously, so have 2 or 3 lights, move the main light in the closest, the fill light a little further back and add a top or back light if you want too.
On a top or back light if you can have direct light hitting the product, (meaning not being diffused through a screen, its better, harder edge, more defines the shape, texture etc.)
For shooting Tshirts, my suggestion is light it more dratically, ( I am talking in a studio here, not on a model ) Low light like during sun set when the sunlight hits an object its really spectacular, not only the colour, but the intensity, it shows teh fibers, the folds, really creates a mood, so play with that kind of lighting and add a softer light from the opposit side or top to soften out the darkish shadows.
Shooting models with apparel, same thing, a great location is good, but your focus is the products, so shoot with a really short DOP ( depth of field) if you have that control on your camera! If you have a beautiful background, it will still come out in the shot, but be a bit soft so your eye or the focus of the viewer is the sharpest part of the shot, your products. Also if you can control the light, make sure the light in the background is slightly darker so the product or model are brighter and they pop off the background ( along with the short DOP ).
Cross lighting again is better for show the fabrics, folds and a "real" of the garments so the viewer can moreso relate to the products and want them or see themselves or thier friends in them.
K.I.S.S. although an old saying ( Keep it simple silly !) is still the best thing.
Just remember if your not a photographer, let a photographer shoot your stuff. There are tons of photogs out thier in your areas ( try craigslist ) willing to shoot for their portfolios' and / or products. They can usually get you models and you just give them some creative freedoms to have fun and inject what you want and at the end of the day, everybody is happy and your have great shots for your stuff. Also most photogs will be shooting digital so you should be able to instantly see what the shots will look like, as retouching is always necessary afterwards, just to clean up stuff.
Thats it for now, feel free to ask me any questions.
thanx
JT