There is no need to risk even small money as a newbie, for experience it is better to use a demo trading account. Once you are confident in making profitable trades, then you can use your spare money.
The demo only helps you to understand some trading features, it will not help you make the same profits when you enter a live account.
Investing and trading is a risky activity, so if you are too paranoid about the risks that exist then please do not trade or invest. To become a successful investor and trader to earn returns, you must consider the risks even if you have to start with a small budget. Do research, learn more and gain experience.
Speaking of Demo accounts, the feelings also is different. In trading using a demo account, you can risk more money because it's a demo only, and the money that you have on that account is just fake. On the other hand, if you are trading using your real money, the feeling is also different as well. I've tried using both already, and I can say that your feeling when using both demo account, and a real account with real money really is different.
I will just add to what you said as well. I've seen newbie investors, and newbie traders out there who are getting overwhelmed because of the lack of information that they have, and because of that, they will just make some decisions base on their emotions, and not on the knowledge into the particular investment that they want to invest their money with. Like you said, do their own research, and if they find a mentor when they're just starting then it would be better because they will make your learning a bit shorter comparing to other people (like me) who did self-study thus, it took me longer time to learn everything (the basics).
Re: Why you should use spare money to invest
This is a very subjective question.
What if many people here are like me who has the knowledge already, but don't have spare money? So you are saying that we will not invest anymore?
I already know the basics already when it comes to investing, but I'm not using spare money whenever I'm investing, but I'm using a portion of my salary to invest. That isn't consider spare money for me. On the contrast, I'm only investing on the safer assets because like I said, I don't have spare money.