There's a few important commands for Skyblock that you'll need as a starting player.
/warp - /warp mine for ores, /warp shop to sell ores and items, /warp ranks to buy ranks with ingame money,
/warp chestshop to learn how to make your own shop on your island.
/is warp (playername) - teleports you to a player's island.
/bal - Check your balance.
/is help - gives you all your island commands, such as /is level, /is restart and /is biomes.
/bar - The possibility to gamble your money for a 50/50 chance of doubling it. Would not recommend doing
this as it's an easy way to lose everything.
/kit tools - Gives you leather armor, a wooden sword and a fishing rod which could keep you safe at the start.
/is sethome 1 and /is sethome 2 - You can use /is go and /is go 2
to go to your different island homes, you
can't set more than 2 island sethomes however.
You can also use /is to go to the first island sethome.
If there's any other command you're unsure of or something you want to do (but don't know how to), you could message me on the Skyblock Diamond server whenever I'm online (or on here if that suits you) and I'd gladly assist you.