First off all i've played many hours of skyblock on many servers and am experienced in economys.
Gun powder price: 1.5 mill for a creeper spawner, returns on average 2 gunpowder each creeper which sells for 6.4$, which means you need to sell 468,000 gunpowder to return your investment which will take on average 3 months when the season is over? Please buff it more or lower the price of creeper spawners.
Iron golem spawners: 1.5 mill for the spawner, iron sells for 4$ each, on average each ig drops 1-2 iron, which means you would need to sell 275,000 iron to return your investment which means the investment would take as long as 1-2 months.
Cactus / sugar cane: Cactus could do with a buff to 5$, at the current rate, it just isn't worth making any sort of cactus farm as it isn't worth your time/return investment, sugar cane could be bumped up to 7$ per same reason.
Blaze spawner: 700k??? and 1 blaze rod sells for 1$???, that means you need to sell 700,000 blaze rods to get another blaze spawner back???? its not even worth to buy them. Plesae buff.
Fast place plugin: Allows you to type /fast place 3 and it'll palce blocks x3 as fast, please look into it, very good plugin for the server.
Add zombie pigmen to the /shop, Having htem buycraft exclusive is stupid.
/tokens need to be buffed, make it so stacked mob all have a chance to drop a head and not just the 1 mob or increase the chance alot, 10 heads for 1 token, and 25 tokens for a key?? that is way to extreme you get on average 1 head every 500 kills in what i have learned with my mob farms.
/boosters, add a way to get boosters they are very good for the server and very benefical good feature,
Add minions, auto grind minions, auto farm minions, seller minions, mine minions would make the server more fun.
Make tinkerer dusts higher %, its impossible to get CE if you only get 5% dust off each book not worth.
Add Cactus chest: 1 chest that fills up unlimited with cacti, very good feature and will benefit lag among other things.
Add mob hoppers and crop hoppers, will collect all mob drops and crop drops in that 1 chunk with the hopper, saves alot of lag to.
Upgradable spawners: Upgrade the spawners to drop for exmaple igs, drop iron blocks then gold then diamond then emearld for a big chunk of money, or upgrade how much they drop, or upgrade how fast they spawn. All spawners, make igs upgrable, and ghasts upgradble and so on.
Make chest sell signs free? No reason for them to be on the buycraft store pretty cheeky if you ask me. or atleast make it so when you double click items in a chest it brings them to your inv and you dont have to get them out 1 by 1.
Add purchasable boss eggs you can buy from the store and you fight it on your island and it gives sick rewards
Add more island pets and less war pets, for example money pet, gives more moeny when selling, farm pet gives more drops when farming and so on, exp pet , mob drop pet etc.
Also harvester hoes.
Will edit and add more when I think of them.