Any amount is fine if you are ready to bear some few losses because altcoins are highly volatile compared to even BTC, as a newbie its better to just buy some BTC for now if you are in haste and then start learning more about altcoins and what makes them have values.
You are wrong because actually bitcoin also has the same properties as thousands of other altcoins that are equally volatile. You can't convince others of an investment that has made you profitable until they really understand how the market works.
I agree bitcoin has more potential than altcoin in the long term, but you have to be willing to be a long term holder rather than just relying on short term speculation. You also can't really profit from bitcoin if you don't fully know how to control your emotions, manage capital, and manage risk during volatile markets.