As of now, it seems like you have a hive with 2 supers BUT NO BEES.
You don't really
need anything else until the bees arrive.
BUT THEN ... you should aim to get to two colonies (so you are more sustainable and daft-mistake-proof --- but nothing is proof against really determined idiocy!) and fairly swiftly.
So that means two hives with oooh at least 3 supers available for each (with frames, etc), and another basic hive (floor/brood/cover/roof + brood frames) for swarm control (and having a poly nuc as well is going to come in very handy one day).
Having the odd empty (even of frames) super spare can also be handy. Even as a feeder eke. (Got any feeders?)
Personally, I like framed rigid wire Queen Excluders, see-through no-hole coverboards,
rhombus clearing boards ... and proper (flat) dummy boards. (You'll be needing a feeder or two, and likely a feeder board, possibly urgently after taking delivery of some bees - so prepare! The 4-pint rapids are the most versatility with cheapness.)
It isn't hard to make plywood feeder/clearing boards and dummy boards (B&Q will cut sheets for free and accurately into your dimensioned parts).. Twinwall polycarbonate coverboards are only very slightly trickier.
But it is simpler to just buy those QXs.
And then, hopefully you'll be borrowing/hiring the association extractor, but needing (at minimum) honey buckets to store it in. (Cheap, but get them before, not after, you need them). Then you'll be needing a bottling bucket, jars and labels ... but if the stuff is safe in decent buckets, it can wait for you.
And of course your equipment requirements would change if you were to move to double brood or brood-and-a-half...
The upcoming Sales are a great way of picking up kit at a better-than-usual price. Problem is that you have to pay for it well before you might need it, then store it, or in the case of JBM, you need to find a place to hide it out of sight of the wife...
One can play cleverly, buying a cheap 50-pack of super frames in the sale, and two dozen DN4 sidebars - so you could make up a dozen brood frames (using the topbars and bottombars from your pack). /// Assuming you are going National - I don't think you have specified your hive type, but the general principle applies regardless.
Don't leave your shopping until it is immediately needed. This last summer, everyone was putting on extra supers and amazingly this resulted in a shortage of shallow foundation. Don't get caught, but don't think you need to stock up for all possible eventualities - cover your plans, and work out how you are going to handle possible alternative scenarios.
Try and keep slightly ahead of the bees - which means monitoring how they are deviating from your Plan A. The further ahead you plan, the greater the potential variation from forecast!