Azur Lane

While the game has a premium currency, they give out plenty of said premium currency for free during extended maintenance and events, so spending money to acquire it is completely optional.

You can buy a pass that gives you a monthly stipend, but gives it to you daily. Like other purchases in this game, this is completely optional because of the previously mentioned free (and frequent) handouts of said premium currency.

Certain events give badges or portrait frames, and sometimes furniture. These items are simply there for bragging rights. They have no effect on the gameplay itself.

There is a login reward system that rewards you daily. These are items like coins, oil, and the occasional bulin to help you rank up your ships.

You can and will end up capping your items and shipgirls. You can use the premium currency to raise the cap, but you usually won't end up hitting the cap often all that frequently, and with there being plenty of free handouts of said currency (mentioned earlier), you don't even need to spend a dime. It's completely optional.

Collab events (i.e. the Hololive collab a few years back) are permanently missable content. But the rest of the events are added into the game permanently after 1-2 years, so if you miss out on a shipgirl, you won't end up permanently missing out on her because she will be added as a permanent acquire later on.

There are login rewards both normally and during special events, but missing a day doesn't set you back to square one. Plus, the rewards you get for login (with the exception of special events) you get are small and can easily be made up by actually playing the game for a stage or two.

The game has daily and weekly missions which are usually things you intuitively do anyway and you'll often complete many of them at a time. In the main campaign you can set your fleets to run through stages with 0 player input from start to end to grind for xp or in game items, I usually set it and forget it while I do something else.

You can buy gems for use in the in game stores, but tbe game is very generous with gems during events and through easily completed side missions, devs will also give out gems as compensation for maintenance delays.

You can buy more stuff to build ship girls and have a higher chance of getting the rarer ones, but the PVP aspect is more of an afterthought, so it's not much of a problem.