I'm working on assets all based in the same style and palette when ready I was planning on distributing them on itch as multiple pages:

Game Packs: Everything for making a theme specific game including:  Tile set, Characters, Creatures, UI, Items and Game Concepts.
Each has unique theme specific elements but shares things like UI and basic elements required to make a complete game.
Examples: Forest pack, Desert pack,  City pack etc.

Element Packs:  Separate packs that contain part of the game packs for a reduced price, for people that just want a certain element without buying the whole pack.
Examples: People pack, Animals Pack, UI Pack etc.

Complete Pack: Includes all Game Packs and Element Packs

Or should I keep it all together for one price and update the pack with new elements.
I'm new to itch and would love to hear your opinions / best practices for sharing my assets.

Here's a little sample of what I've been working on:

Keep in mind that someone who buys one product gets access to all files uploaded to it, even in the future. That includes all files with special prices as long as the buyer has paid the minimum amount to access them. You might want to make each asset pack a separate project, and make regular bundles with reduced prices that bring all the asset packs together. That however could be a problem if you have a lot of them, since there's a soft limit of at most 20 projects you can have. So it depends. Hope this helps!