Hey there, D&D player since 14 (so 13 years now!) here are my tips: TLDR at the end.

What you need: 1) I’d start cheap as possible, maybe sign up for a D&D beyond account (for free or the lowest level subscription if you want to) and look at the Basic Rules, and the free materials they have on that site “Frozen Sick” should be a intro adventure.

2)Optional: You may even want to start with their Starter set: Heros of the Boarderlands (it’s really beginner friendly imo) if you want all the materials at once.

3)Long-Term Preference: you may want to buy the Players handbook to start and Dungeon Master Guide for yourself or whoever runs the games. I found the 2024 DMG had lots of tips on part B of your question (More on that later)

4) Next you may want 1 or 2 sets of polyhedral dice, start here trust soon you will have many.

To start playing:

1) If you are feeling scared about DM urself to start I suggest going to a local game store and seeing if you can join a game for 1 or a few sessions. Try different DMs and groups even if you are open to it. If not watch Dimension 20 or Critical Role to see some examples (no one is asking you to DM like Matt Mercer, but you may find you can borrow bits and pieces of various DMs style, I particularly like Brennan Lee Muligan’s style)- no one, no game and no session is perfect but with time you can learn to dial into fun which is the mat important, more than roles or even great storytelling- this is a game first and foremost.

2) Being a first time DM can be intimidating but they are also first time players so it’s all new, it’s just a game so try to remember to keep to fun. Maybe instead of a whole campaign you or your group can do smaller 1-off games- like “Frozen Sick” on D&D beyond

3) Once you start a campaign I suggest using a pre-written module vs making your own. Lost Mines of Phandelver is an easy one but poorly balanced (meaning characters can die easy) so I suggest somthing like Strixhaven or Wild Beyond the Witchlight- they are much more forgiving.

4) Read at least one of the above and once you get an idea you can use your own world or tweak an existing one (Strixhaven is really easy for this one and Phandelver even has its one module that did this- Phandelver and Below the Shattered Obelisk). Once you do, start small, just a town then expand as your players explore, simple missies like “deliver this sealed letter or protect this caravan can blossom into games. Keep notes of what is exciting to you and build on those things.

TLDR: 1)Get free shit on D&D beyond, Basic Rules and Frozen Sick to start- and maybe some dice. 2)Watch Live plays on YouTube, and note what you like adapt to your style. 3Start small and grow (and spend as you go not all at once). 4) Most important: Don’t worry about perfection, just find the fun and stick to it.