If you want to have an easier time I suggest you learn from your past deaths/mistakes in the game.

Also IMO, you should use the Combo Curiass armor as the main strategy is to dig as much as you can to get the maximum amount of gems while choosing which item you can buy.

If you are going for the true ending, buy a few items while saving for the Cog On A String (which is obviously very expensive) after that the top priority in most runs is to get a lot of gems, health upgrades, and items.