DO NOT ENTER THIS GIVEAWAY.

Oh no. Your soul. It's now forfeit.
I can't say more.

1000, if I remember correctly.

It's capped at 1000. Unfortunately, that's not anywhere near the sum of what you'll get from lower level public giveaways- in fact, you can make that total up in a single day of giveaways. If you're doing high enough levels it could potentially be a functional approach*, but it's much easier and more functional to put into forum giveaways or into groups.

( * Though, keep in mind, even at level 5 you're likely to see only about 10% of users actually reading descriptions, and entry counts that are regularly in the 800+ range, so a fairly high level restriction is needed before you can reduce the numbers enough to work within a "mere" 1000 user limit. )

Given that there's still a sizable number (and a significant reduction per step) in exploitative, rude, and/or rule-violating users up until level 4 (or level 2 for forum giveaways), anything below that tends to be unworkable in the long run for any kind of reliable management. By level 5, you end up seeing issues like Non-Activations and Multi-Wins becoming fairly rare, and by level 6 they're pretty ignorable. Thus, it's more popular to rely on level gating alone, when it comes to public giveaways, than to struggle to manage numbers that blacklist cap doesn't permit management for [ie, by trying to filter out lower level users for things like not reading].

That said, you do get exploitative and rude users all the way up through level 10, so level gating past around the level 3~6 range tends to just needlessly exclude reasonable users, so there's definitely merits to having some sort of filtering system in place (as per the implied one contained within this giveaway) at those levels. Of course, an even more reliable and straightforward option is to utilize SGT filters or self-filtering groups, as you can balance filtering and inclusions/exclusions to work better to your considerations, as well as likely limit the entrant pool to a much more manageable total (though, of course, that ends up being a restriction in itself).

In short, while it may or may not be the strategy that's most "nice" for the OP, from more generalized perspectives it's not considered a very functional one (as indicated by the community considerations such approaches have received in the past). Again, that's mostly due to the blacklist cap (though the demands on time and effort for managing such large blacklists does disuade many). After all, given that the 1000 limit can be filled (and then some) with just with bigots and fully exploitative and/or abusive users alone, it's a situation that has long had users pushing for an increase on blacklist limits, even before considering the more significant demands that'd come from utilizing blacklists for public giveway filtering purposes.

TL;DR version:

it is a bad idea, because your BL will be full too soon.