Synergies

[Rasg0s]

The one thing that bothers me into not playing this game is that I dont know what items can be combined or what does synergy. Is there a way to know in-game?

[Moonbane]

Once you find the relic in the western end of the Inlaid Library that is the second level, the game will begin to record your collected evolutions. And items good for anything you have will eventually be listed on the choice screen, like spinach for the fire wand.

Your collected evolutions can also be viewed on the pause screen.

Edit: But from the sound of it you are not that far yet, so you can make use of this page:
https://vampire-survivors.fandom.com/wiki/Evolution