I also don’t like ad-filled apps, that is why I normally buy my apps.
I have used Diaro before and it was quite good. It could save your entries in iCloud or Dropbox and have apps for almost all platforms. I have also heard good things about Day One.
I played with the app for a bit and I think it is good enough to start with. If you don’t have the baggage of trying to import from a different app I think it should be good to go from the get go.
I would have liked it if it could have shown my memories on a map and I could go look at my entries at a specific place etc. It currently only filters on if things are there. Not on the details of what is inside of those things.
But I think it is a good place to start from regardless. And the ability to share things directly with the journal is quite nice. I have already done it with some of the memories generated with the photos app, so I would assume anything can be shared with it.