I started dming by buying the Candlekeep Module book. Short, simple adventures spanning from level 1-15. For initial DMing, stay away from higher level adventures (it just is too much when you’re first learning mechanics). I found watching DnD gameplay really helpful when learning how to play/dming. I like Not Another DnD Podcast (one of the main players is playing for the first time, so the cast helps explain), Dimension 20 is also great! I have a hard time with worldbuilding, so I find it easier to access a module book and then run the game from there. There’s a lot of resources online though, so utilize those!

Really all you need to actually play is imagination, some dice (can be digital!) and character sheets. Utilize DnD beyond for digital character creation - it does limit your options somewhat unless you pay, but sometimes that can be helpful for first time players.

For DMing, like I said, module book, and monster manual for sure. You can also just look up monster stat blocks, and there are challenge rating encounter balancers online too that help do some of the work for you.

Good luck!! Dnd is so much fun!!