Here are some ideas - not necessarily in order:
- Decide on the game - what type of game are you making (Gacha is an element in the game, not the game itself)
- Plan the game in detail - how many levels - what are the chance awards the player will get - how will it help them
- Choose which software you're going to create the game in (e.g. Unity, Clickteam Fusion, GameMaker, Godot etc.)
- Learn how to program using your chosen software
- Purchase graphics, download graphics for free, or learn how to make graphics yourself
- Start making the game
- Add in music and sound effects
- Test the game - then test it again
- Fix all the bugs
- Release it