use the demo to see if you like the platform and then use the platform you like to trade real money micro stakes. the fills your orders get on a demo will not go through the same tolerance checks as real money trades and as a consequence your demo performance will be different to your real money performance.
making money on a demo is not a given that you will make money on a live cash account, the 2 accounts are not like for like. the stop loss order fills wont be slipped so much and that demo trade where you double down and double down to chase a big loss isn't something you'd have the bottle to do on a live cash account.
the 2 are very different. a demo will show you the functionality and tools and platform lay out but don't expect your amazing trading performance on a demo to carry forward to a live account when you finally make the switch.