At least 2 hives & 6 supers.
To explain - for a single colony you need a hive and a spare hive (for swarm prevention purposes).
Your bees may well be so prolific (most are, but Spain - I don't know) as to need more than a single basic Langstroth 'medium' box as a brood volume. Two medium boxes or a single jumbo is more likely.
You can do swarm prevention (sometimes! - but probably not from a double-brood colony) with just a nuc box, but you are going to need another brood box to recombine them - the nuc won't stack with the rest of the hive, hence the second hive using an identical brood box rather than a nuc as the 'first spare'..
With one colony, you are vulnerable to beginners' mistakes terminating your colony (unless you go begging to a friendly and reliable local beekeeper running similar hives (thus frames). Two colonies is the sustainable minimum; you should aim to get there as soon as possible.
Supers. A hive can quite feasibly need 4 (more if you are very lucky) supers at the same time. If they get full, you are going to need to extract some (early) and return them for a refill. But while they are off the hive, you need to still give the bees some space, hence extra supers are worthwhile.
As the number of your colonies increase, the amount of spare equipment 'cover' becomes proportionally less. But it is essentially 100% spare with one hive.
Spare brood boxes and supers aren't any real use without frames to fill them. If you wanted to keep one super empty for now so that you could use it as a feeder eke etc, that's fine - until it is the only spare super you have!
Your principal hive could do with a queen excluder (for your sanity), a syrup feeder of some sort, and likely some winter protection - whether from mice, woodpeckers (and other birds) or bears!
You need a suit, wellies, washing-up gloves, smoker (and some sort of fuel), a hive tool (or two),
washing soda (be careful with the spanish translation of that), a couple of buckets with lids and from then on its personal preference additions (like a water mister) or things you don't need yet (like honey containers, and queen-marking cages) or things you hope you can borrow/hire rather than buy for yourself (notably a centrifugal honey extractor).
There's quite a lot of kit going to needed, if not on day 1, then before the end of year 1.
And you need to read some good tutorial books by different authors - and get in among some bees, (and ideally stung) - before you buy
anything financially significant.
