The Monster Manual feels essential, but how often do you really use it at the table? Once a creature is chosen for an encounter, you typically write down or print out its stat block. The book itself often stays on the shelf during play. For a new DM on a budget, using online SRD resources or even a PDF of basic monsters for your first few sessions is totally feasible. The PHB is the only book players will constantly ask to see. The DMG is mostly for prep. So, if budget is a constraint, prioritize the Player's Handbook and consider the others as 'soon-to-be-essential' rather than 'day-one-essential.'
Graphic novels and comics! The Drizzt comics from IDW or the older Dragonlance comics are a fantastic, visual way to get into the stories. They condense the key plot points and give you a face for the characters. You can blast through the adaptation of 'The Crystal Shard' in an hour. If the story grabs you, then you can seek out the full novel for more depth and internal monologue.
It’s a low-time-investment sampler. The art style sets the tone, and the action is immediate. This is how I got my younger cousin interested. He’s not a big prose reader, but he devoured the graphic novels and then asked for the actual books to get 'the rest of the story.' It’s a perfectly legitimate gateway medium in the modern age.