This is quite tricky to automate so the best solution I could find would be to add actions to trigger when a screen loads.
So throughout your app you can add points to a ‘points’ field for logged in user (or XP, whichever you prefer) by setting an action to ‘logged in user points’+10 (or however many points you want for that action), then you can edit a rank text field in the user collection to a word of you choice such as Beginner, Expert, Legend when the page loads.
So when a page loads, set the following actions (you can add whatever name and whatever points range you want here by the way, these are just examples):
Whilst this does not currently link with a Rank collection, it can work alongside the rank collection as long as the Rank field name in the user collection matches the name in the Rank collection.
Have a look at the cloneable example I did for you Ranking example