BASED ON MINI ACCOUNTS
Oanda offers maximum 50:1 for normal pairs; 25:1 for exotic pairs
FXCM offers maximum 200:1 for both normal and exotic pairs
Saxo offers maximum 100:1
Avafx offers maximum 200:1
The higher the gearing/leveraging, the higher the risk. Oanda's 50:1 is good for beginners and for those want to take lesser risks.
Not necessarily actually.
Say you have USD1,000 in the account.
Now you have leverage 200:1 and 50:1.
And your system is to buy/sell at USD10,000 units each time.
At 200:1 you need only to use USD50 as maintenance margin; whereas
at 50:1 you need to use USD200 as maintenance margin.
As to how much one would like to trade, it depends really on the individual. Doesnt mean the individual must trade all that is available.