'Purchase for use' is the act of buying cryptocurrencies for use in shops and person-to-person transactions. This carries very little risk if you only buy what you need, and if you do not hold onto what you bought for longer than needed.
'Speculation' is the act of buying a reasonable amount of cryptocurrency, with money you can afford to lose, and holding onto it for the long term. Speculation must always be done with the knowledge that you can lose everything you put in.
'Gambling' is the act of frequently buying and selling cryptocurrency in response to market fluctuations and "hype" in the media and other sources. It is frequently irrational, and almost always results in a loss of money and financial issues.