I'm also going to recommend
The Battle Cats. It's like Age of War, but you send cats (and waifus) to fight various animals, and it has a surprising amount of depth to its gameplay.
Quick summary:
- No forced ads
- Really generous with its premium currency (cat food)
- Best units are unlocked by beating certain stages
- Common gacha units are more useful than the rare ones
- You can predict your gacha rolls with 100% certainty using a simple webiste
- Has been receiving constant updates for 13 years now
The biggest flaw this game has is that you will have to use the wiki a lot.
Another recommendation I can give is
modded Plants vs. Zombies 2. Plants vs. Zombies 2 is a tower defense game where you plant plants in your front yard to defend against the oncoming zombie horde. Unmodded PVZ2 has become bloated adware, but the modding community has salvaged it and made quite a few gems. These mods are free and have no ads or in-app purchases.
PVZ2: Alternate UniverZ is currently one of the best ones out there, and it's relatively easy to install: just download its APK file from Google Drive. It completely overhauls the game and has a lot of custom content.
PVZ2: Reflourished is the closest you can get to vanilla PVZ2 while actually being good. It also has a tranny virtue-signaling in the form of a cosmetic item.
There are other mods out there, but installation for some of them can be a hassle, and their gameplay can get notoriously difficult.