There have been several threads about cheap brokers so I would suggest doing a search. If you only have a few hundred to invest then I don't think you should be buying shares as the transaction costs will make up a huge percentage that would have to be recouped by capital gains.
If you don't know what you are doing when it comes to selecting shares then you should also not try picking stocks but rather stick to cheap tracker funds. Just because buying and selling of shares is easily done by the click of a button does not mean that it is easy to select the right investments.