Use Spread Bets to get comfortable with margined products.
Spread Betting also uses margin but its advantage for beginners over CFDs is trading positions can initially be kept small. For example, if you buy the FTSE 100 risking £0.50 a point and the market moves 150 points against you, the loss is a manageable £75.
So open a spread bet account, fund it with £200 - £500 and try to trade between 2 and 10 times a week with small stakes. Then if you lose it won't matter too much as your losses over a period of time should be no more that £100 - £300.
Plus, don't discount the benefit of losing money as it's often a great educator, ie it tells you what you're doing wrong and perhaps what needs to be addressed, for example -