For example you have 1000$ on your deposit. You should invest under 5% 1000*0.05=50$ <<< it's your maximum risk 50$\22pips=2.2 <<< how many pips are your 5% or 50$
So your lot should be 2.2 (Consider that on different broker NOT MAJOR pairs has different value per 1 lot!)
Best option to invest 2-3% and than add more lots in already winning trade!!!