There are several oppportunities that are available to start building a crypto portfolio even when you have no capital, particularly when the investor is willing to invest "sweat equity" to build up their portfolio and grow it.
Airdrops
Airdrops are when an investor receive free shares in a new coin that is in the process of being freely distributed to new share holders. An airdrop is a true giveaways where little or no investment is required on the investors part. The best website for locating these opportunities is AirDropAlert, Requirements differ considerably. Sometimes you have to prove that you own bitcoins. Other times you need to show you are Junior Member on the BitCoinTalk crypto forum. Other times you just have to download the crypto coin wallet software and then request the airdrop shares from the lead developer. PS beware of possible malware!
Why would shares of a crypto token be given away? The reason is because a coin only has value if the network of users/holders grows. The value of a crypto token is said to be directly proportional to the square of the number of users based on Metcalfe's law. Therefore, there is an incentive to give away tokens and in doing so build up the long term value of the network. Several well known crypto currencies that have been airdropped and have appreciated greatly (500%+) include Byteballs, Decred,and NEM. One current airdrop is coinstarter which is a Waves asset. You can obtain free coins from my referral link at coinstarter signup.
One other airdrop is JesusTokens at this link JesusToken Airdrop. Please accept my apologies if this offends any readers from other religions. The charitable spirit in this crypto token is promising and is why I elected to participate and promote. 🎯
Bounties
This is where you get paid to do a small job such a translating an announcement for a new coin into a foreign language or you promote the coin to your Facebook or Twitter followers. The advantage is that your labor is paid out in a crypto coin that itself may be undervalued and you may benefit from future appreciation of the coin if the coin is successful. One of the best places to find these opportunities is on the Bitcointalk market place.
Signature Campaigns
Many promising coins including Ark, Bitsend, Deep Onion, Zencash have signature campaigns where you are incentivized to wear a signature on your bitcointalk.org forum postings Depending on your rank on the site (e.g. Junior Member, Full Member) you will be paid out a higher number of tokens for your effort. There may be a requirement such as 10 or 14 posting a week, thus some modest degree of work will be required. You might be paid weekly in shares of the coin that you are promoting.
Mining
This is where you earn coins by processing transactions on the blockchain network. You are paid for investing your computer hardware, your electricity and your brain power. Most of people think of bitcoin mining but this is highly competitive due to too many sophisticated players investing in the business of bitcoin mining, but is possible to do mining of Monero and other smaller lesser known coins with basic equipment such as laptops. Here is a video to help you get introduced to the business of crypto mining.
Investing Small Amounts
Finally, there is nothing to stop a new investor from starting with small amount amounts of capital. Even $50 or $100 invested in a well chosen coin or portfolio of coins could lead to very good returns, as can be observed from the long term price charts on Bitcoin, Dash, Litecoin, NEM, etc.
Here is a dated article but still useful. http://www.cryptocoinhome.com/how-to-earn-bitcoins-with-bitcointalk-org/
As always good luck with your investing and I welcome your questions. 😎