The quickest your going to loose that 700k is to open a CFD account and follow the daily thread!
If your TA/seasonal trading skills are up to scratch and you have experience and a strategy that works you can consider playing high priced warrants but with 700k you don't need to jump in and out to make good money...!
Just my 2c
A
Yes I actually agree here with you Argento but that is why I asked first the level of risk he is looking at for this lump sum.
In any event, whatever you do, make sure you know how to operate the instrument, ie CFDs in this case and and second and most importantly pay very careful attention to risk management.
its not because of CFDs that traders lose - its because of poor risk management.
If you disciplined and never risk more than 1-2% of your capital on any given trade and never move stop losses, always have target prices, then you can learn while you play.
I'm not a fan of demo accounts for learning. You need to have skin in the game.