I advise you to read Byron's stickies- you'll need to make sure you can take care of the plant's needs (fertiliser, lighting, etc). It's not expensive by any means, but you want the plants to be healthy.
Plants that do well without fertilisers (other than fish waste):
Java fern (narrow leaf java fern is good for small tanks)
Anubias (nana or nana var petit are good for a 10G)
Plants that are easy as long as you have proper lighting and a fertiliser like flourish comprehensive (check byron's stickies)
Echinodorus Bleherae 'Compakt'
Plants that may require trimming but will fill in large areas quickly(ie stem plants)