You have just understood, the choice of your SSL certificate will depend on your needs. If you have a simple website with a single domain name, the certificate provided by your host within your offer may be sufficient. On the other hand, if your company has an e-commerce site with a certain notoriety and several subdomains, you will have to invest in an SSL certificate.
The easiest way is to ask yourself the following 3 questions:
How many domains do I need to secure?
What kind of site should I secure?
How much importance do you place on the trust of your customers?
Then you have to set a budget (that's important, you will agree!) But remember that depending on your activity, it is an investment that will make profitability in notoriety.