How do I invest in decentralized crypto?

Could you elaborate on the steps I should take to invest in decentralized cryptocurrencies? As a novice in this field, I'm uncertain about the process, the risks involved, and the best practices to ensure a secure and profitable investment. I'm particularly interested in understanding the differences between centralized and decentralized cryptocurrencies and why investing in the latter might be a good decision. Additionally, I'd appreciate some guidance on selecting a reputable exchange or platform to make my initial investments.