You should not consider buying shares unless your buying £500 or more IMO.
If you bought just £50 then you will have probably around £16.00 worth of Fees - Stockbrokers fee and Stamp Duty, that means your shares have to increase by more than 30% before you even break even which is quite a large move.
As many people have said, the stockmarket at the moment is very volatile, i am trading in a particular stock that has had fluctuations of 60% in a day so although this volatility could create some great value stock it may also lose you a lot of money and quickly.
Also btw, you have to be 18 to trade in stocks so it would have to be done in your parents name which may cause a problem if they own any stocks - Capital Gains Allowance.