All Basic Commands you needed.
-Clear potion effect
-Kill All Entities
-Give {Barrier,Command Block,Dragon Egg,Mob Spwaner}
-Difficulty {Peaceful,Easy,Normal,Hard}
-Gamemode {Survival,Creative,Adventure,Spectator}
-Timing {Increase time by 1000 ticks,6:00AM,6:00PM}
-Weather {Clear,Rain,Thunder Storm}
-Set Spawn Point
-Gamerule {sendCommandFeedback,commandBlockOutput,Daylight Cycle,Keep Inventory,Random Tick Speed(0/5/100/1000/10000/normal)}
-Index on last page if you couldn't find somecommand
All command have description found by hover your mouse over it.
Thanks for using my command,
MixzerZ