I usually prefer text to video tutorials, but for me one of the best introductions to Grid was this video from Mozilla:
https://www.youtube.com/watch?v=KOvGeFUHAC0
Seeing it like that really made me appreciate how much boilerplate Grid could let you cut back on.
Also "Flexbox Froggy"
And its grid counterpart Grid Garden.
https://cssgridgarden.com
- A Complete Guide to Flexbox: https://css-tricks.com/snippets/css/a-guide-to-flexbox/
- A Complete Guide to Grid: https://css-tricks.com/snippets/css/complete-guide-grid/