First those free gloves are not to be used on heavy bags, despite the fact that they gave them too you with them.
Next, get some hand wraps, good ones, not the short everlast ones most sports stores carry. I like the mexican style ones. And learn how to wrap your hands ( http://innovativema.ca/forum/view.php?pg=wraphands
And last, the best bet is to just use boxing gloves, I like 16 oz gloves for both sparring and bag work. The extra weight gives you a little extra for the workout, and keeps your hands safe.
If you want a lighter pair look to MMA style gloves, the Harbinger style are nice. Easy to find ones are the Century wrist wrap ones.