A smooth finish is essential or you'11 snag yarns. The dowels should be well set. Two sided looms are usually flimsy and awkward to use - one sided looms with projecting dowels are best. The loom should have a base, so it stands on its own. Light or heavy is a matter of taste - heavy is more stable, light is easier to move.
Price is no gauge of quality.
But be willing to pay for a good one - it should last forever and always be a pleasure to use. Here's a simple project to run through basic techniques. Modify it however you wish. If your loom is very different - read the instructions through and adjust them as necessary. If your tension bar is in back, tie on the front dowel, for instance.