The ideal initial amount is 0 (zero), you earn some coins in airdrops, giveaways or doing some simple tasks online and then you build your portfolio from there.
That's how you really learn to navigate in bitcoinland.
If you have enough money to invest, money your can afford to lose, then just buy bitcoin every month, sit on it, and in a few years you'll have a nice sum of money.
Thanks for the response. What are airdrops? and what examples of giveaways and where to source them?
Follow these 2 sections:
Announcements (Altcoins)
https://bitcointalk.org/index.php?board=159.0Games and rounds
https://bitcointalk.org/index.php?board=71.0Search for topics with 'Giveaway' and 'Airdrop' in them, if you don't immediately qualify for them, plan for the future.
Also search for bounties in altcoin announcements and check if you can do any of them.
Some of these don't worth your time, some do.
Careful installing new software on your computer like new altcoin wallets, they may have malware, improve your opsec.
Good luck.