General networking database help

I want to make my own turn based strategy game with some minimal RPG elements. It would be kind of multiplayer. Obviously I want character stats, items etc server side, and multiplayer is a given.

Using about 30 different market and craft items, 12 types of armor and 12 kinds of weapons, each player account would have a max of 30 troops at any one time, and 1-4 active skills to choose, with about 8 stats, plus exp and level entities, whilst having a lineage so new characters can take over etc.
tldr; that’s about 90 or so entities.

I’m trying to figure out what kind of a networking system I should use. Like google play cloud, google cloud datastore or a regular database.

I’m not sure which to go with and definitely want something cheaper that still works.

Was wondering if someone had experience with android/google network systems and could tell me what they used and possibly know an average range per month for 90 entities and around 15,000-25000 players to start.

Bump

tldr;
database or cloud that’s the least cost for turn based rpg with 7 troops per player
multiplayer pvp
For 25,000-50,000players
max 110 entities?

would 1TB storage do?
What would the out/in GB/month look like?
Bytes per entity?

can I have market items set in an array to make them all from one entity?