Every charm has its use, even if you don't think you'll need it. Buy them all. If you haven't already, buy all charm notches from Salubra and get the latern, that's a big expense early-mid game. Collecting mask shards to increase health and vessel fragments to increase your soul vessel is mostly a matter of exploring. Seriously, explore everywhere. If you can't access a place, mark it on your map (buy more markers if necessary, another thing to spend a little geo on).
Those grubs (green worms) you're saving go to a room top left of the main column in Forgotten Crossroads (the one with all the platforms and flying bugs), where you can collect your rewards. Always try to save them. Some might not be reachable yet, so mark them for later. Sometimes the distinctive grub sound will lead you to discover a hidden passage or broken wall behind which you can find it. The rewards are worth it.