I never suggest any free vpn if you care your data just avoid them they keep logs and sell all your data to third parties.
Your ISP may already be collecting and selling logs, (the US Congress passed a law explicitly allowing them to do just that) and your ISP will know much more about you because you gave them a ton of personal info when you signed up.
It's a matter of who you want collecting your connection metadata. I prefer a nearly anonymous VPN provider do that. All they know about me is my email address, ISP provided IP address, and maybe a payment account, if I use a paid plan.
If your web sessions are 'https' secured, neither your ISP or VPN can read the content of the websites you have accessed, or the pages that you looked at because thay are encrypted. However, they will see the domain name that you connect with, as they do need that metadata to establish the connection.