1) Discount on all items in the store for the first few days or so, to allow users to race ahead of the competition and acquire items that they may have lost due to the reset. It'll be nice to see say a 10% off discount for the first week or so, seeing as it'll encourage everybody to start early :)
2) The last Skyblock map's spawn had a marketplace, and yet there was no life there. The place felt more dead than a 500 year old tortoise. Perhaps add NPC's behind each market tent, all in which sell different things? (i.e. fishing rods, flint and steel, dirt and grass). I reckon that having these kinds of items sold by an NPC will make the spawn feel more 'alive' whilst simultaneously providing incentive for people to go there.
3) Now for my big suggestion..
Higher-leveled spawns that provide higher-leveled content
The nether, since release, has been a complicated mess with a tiny box hut for a spawn.. boring! Perhaps only by completing most of the medium challenges, you can gain access to the nether, as well as access to the command /netherspawn, and it'll be a re-skin of the main spawn but with upgraded content (i.e. as previously mentioned, there could be a marketplace, however rather than an NPC selling dirt, they could sell mycellium, or rather than selling a fishing rod, they could sell an unbreaking enchanted rod). There will be numerous ways to leave the open-world spawn, and venture into the nether as usual, where you can discover a randomly-generated world as tradition.
Similarly, the command /endspawn could be unlocked upon completing all expert challenges, and in this spawn we could see a more dangerous approach, with PvP being enabled in some areas of the spawn, endermen roaming freely and of course, another upgrade to the marketplace (i.e. rather than mycellium, an NPC could sell podzol, or a LotS fishing rod), all within a re-skin of the main spawn.
I know that this suggesting may not be the best explained (tbh I rushed it because I forgot to make it yesterday), but if you would like a more in-depth description of the idea that I had in mind, just say so and I'll work on an essay describing all of the potential features that a system like this may have.
