Hi,
The point of using Android (with more or less Google services in it) is that you would have a phone compatible with many apps. If you think that you will use apps, and especially special ones (like for your bank, to purchase bus tickets, etc.), using Android will be easier.
Sailfish and Ubuntu have the advantage of being Google-free, which means that they don’t depend on Google for the updates (if I understand correctly, they are still built on top of Android, but someone techy could explain it better). And it feels better for the spirit if you are looking for open source software or non-monopolistic systems.
I would advise you this:
- Think about what you will do, need to do or want to do with your phone. Is there an app you absolutely must use, for example? Do you plan to chat with friends using a special app (Whasapp - don’t!!! –, Telegram, Signal, Conversations, etc.)
- Try to take a look at Ubuntu, Sailfish and Android in action (perhaps a Fairphone angel lives next to you). Or at least check videos on their respective websites.
- Try out the systems for a while: one month on Ubuntu, one on Lineage (or Fairphone Open OS, or /e/), one on Sailfish.
As it is your first Smartphone, as you are not yet (I guess) in need for special apps, and as you want to avoid Google, I would advise to start with Ubuntu and Sailfish.
Enjoy your phone!