Here's some of the server plugins that you can use (link to site, command in-game, description):

• Advanced Timber - press shift while chopping trees to fell the whole thing at once
• Auto Doors - /ad - create big auto-opening doors without redstone
• Backpacks - /bp - create backpacks of different sizes
• Chisel - create a tool to rotate terracotta blocks, stairs and other blocks after they've been placed.  Uses iron and a stick.
• ClickSort - sort your inventory or chests with a single click
• CraftPlus - craft horse armor, grass, nametags, string, webs, ice...  crafting the uncraftable
• Daily Rewards - log into the server daily and receive some bonus swag.  Diamonds, emeralds, cash.  Lots of cash.
• Editable Signs - shift-right click to edit an already placed sign.  Also allows you to use color codes
• GriefPrevention - claim your land with a gold shovel or by placing down your first chest.  Buy more claim blocks if you run out.  Info here.
• Marriage (Reloaded) - /marry - Share a home, get XP boosts when together, /tp to each other and share health
• Melt Down - get back (proportional to remaining durability) ores you used to craft armor and weapons
• Mineable Spawners - silk touch allows you to sell or just relocate a spawner to wherever your mob farm is located
• Pet Master - /petm - displays info about pets, and lets you manage your pets, set them free or trade them.
• QuickShop Reremake - place down a chest and hit it with an item in your hand to create a simple chest shop for selling.  Shift-right click to change options or remove.
• Repair It - /repair - for a cost it will allow you to repair tools, weapons and armor
• SimpleCompass - /scompass - displays the compass on the top of the screen.  The command brings up options for you.
• Steam Baths - create a pool with lava under glass under water and relax to regenerate health
• SmoothSleep - allows single users to sleep on a multiplayer server.  You can regen health, feed you and remove potion effects while you sleep.
• Time Is Money - earn a paycheck for playing!
• TitleManager - /tm - displays the scoreboard on the right side with player info.  User '/tm sb toggle' if you really don't like it.
• VeinMiner - /vm - hold down shift while mining to break the entire vein of ores or minerals
• Wailat - What Am I Looking At?  It's the thing at the top that tells you what you're looking at.
• WildTP - /wild - allows you to tp randomly anywhere on the server.
• EXPBank - store your XP for enchanting your diamond armor later

A couple of tweaks and datapacks from Xisuma:

• Datapacks: AFK Display, Anti Creeper Grief, Anti Enderman Grief, Anti Ghast Grief, Double Shulker Shells, Dragon Drops Elytra, Gravestones, Larger Phantoms, More Mob Heads and Nether Portal Coordinates ('/trigger nc_inNether' or '/trigger nc_inOverworld' to get proper coordinates of where nether portals need to be constructed to link between worlds)
• Tweaks: 12 Trapdoors, 4 Bark Blocks, Back to Blocks, Black Dye with Charcoal, Craftable Gravel, Double Slab Crafting, Dropper to Dispenser, More Bricks Crafting, More Stairs Crafting, Renewable Coral Blocks 2x2, Rotten Flesh to Leather, Sandstone Dyeing, Uncraftable Ice, Uncraftable Nether Wart Block, Universal Dyeing, Wool to String.

And plenty of quality-of-life plugins as well:

• Advanced Achievements, Blood in Minecraft, ChatControl, DeathQuotes, Dynmap, EssentialsX, FastLeafDecay, GiveMeArms, HealthBar, HorseTPWithMe, Inventory Rollback, LuckPerms, Matrix, MoneyDrops, Pickup Arrows, Protection Time, Redstone Waterproof, ServerInfo, ServerList Plus, Vault, WorldBorder, WorldEdit and WorldGuard.