I spent a ton of hours on Flight Rising. It blends collecting, battling, and customizing in a cool way, and the community is pretty active too. Among all the free games I’ve tried, it’s the one I keep coming back to. The economy and breeding system can keep you busy for days without spending anything.
I spent hours on one where you raise creatures and trade them with others—super fun community and surprisingly deep for a free game. Loved decorating my little space too.
I also enjoyed Neopets. It's a kind of game where you are able to take care of your pets and play with them. You can also visit different places in Neopia.