Permanent and Quick Option for Teeth Gap?

Bonding the teeth to disguise the gap between them is a good option in some cases. You want to make sure that your teeth are the right proportions to accommodate this gap. By that, I mean that if you already have short teeth or wide teeth, adding bonding to the sides to close the gap will only make them look shorter and wider (and unnatural). Keep in mind that bonding is a good option that will last you but can discolor over time due to the nature of the material used. Another option that is much longer lasting would be to get porcelain veneers on these teeth, if you are a candidate. 
With regard to the bands you mentioned, I would never recommend a patient to do any sort of orthodontic treatment (moving the teeth with bands, for example) at home. It can damage the teeth. Even if you were to do it at home and were able to move the teeth, the space that was once between those teeth will just be transferred to the sides of them, so you will still have a space. Also, Once you take the band off, the teeth will drift back to their normal position if they are not being retained. Hope this helps!

A 3mm wide space between your front teeth is a great candidate for dental bonding as long as your teeth are long enough to accommodate the added width. If you start out with short teeth with a 3mm gap, then trying to widen the teeth will make your front teeth look too wide. Dental bonding is the most conservative procedure we do as dentists and it can last for many many years, but no procedures are predictably permanent. Certainly stay away from do it yourself orthodontics!