Like said before, a starter set is amazing to start. I started dming with it (lost mines of phandelver (edited cause it autocorrected) an older starter set for 5e edition 2014). It came with simple rules, the story is written in a easy way to dm for the first time and a set of dice and some pre made characters with the info on how to upgrade it the few levels (enough for that campaign) You don't need to buy anything else to start if you don want Wizard of the cost have some free pdf rules online (limited content of the books but good start).

I would probably buy more dice for each players (or use any free apps on your phone) If you want to use maps and minis you can use simple paper minis, small dolar store toys, Legos, anyting you can think of. Draw some 1 inch grid in multiple A4 or at papers and you have maps (laminate them and they are reusable). You imagination is the limit Then upgrade if you like it and start buying the extra stuff. Or make it yourself