first start with GSC:

the place where u go to mohagony town to ice path, theres a lake right? in the middle of the lake theres a grass patch in the bottom line just look for a hidden ether or elixer

then start with LGFR:

this page of walkthrough says if squirtle starter gary has lv 35 gyarados and lv 38 growlithe but its actually lv 38 gyarados and lv 35 growlithe. i noticed it when i was playing at silph co. now

now with either FRLG or GSC:

in saffron the mimic house, theres a nugget inside the girls room. its on the desk beside her pc

ill edit more later