foley and field recording samples are crucial af to basically everything i make at this point lol. they add so much texture and depth and can be really effective percussive tools if you use em right
all the resources people have mentioned so far are great. i can't stress enough how helpful it is to have a microphone with you (even a shitty one) to record whatever sound might come into your mind, or to just take with you on walks and pick up the sounds of leaves rustling, water, etc. plus if the microphone sucks, the artifacts in the low-quality sound could actually be used to your advantage.
i'd be willing to put together a .zip of some foley/field recordings i've collected from friends and recorded myself (it wouldn't contain any material that's illegal to share), shoot me a PM if ur interested :^)