Have you just started up a creative world and have to take 5 minutes to set the gamerules to what you want? Well, using the power of the new 1.12 toolbars, you can save this command to a command block! The command for what I think are the perfect gamerules is here: /summon falling_block ~ ~1 ~ {Block:command_block,Data:1,TileEntityData:{auto:1b,Command:"fill ~ ~ ~ ~ ~-1 ~ minecraft:air"},Time:1,DropItem:0,Passengers:[{id:"falling_block",Block:repeating_command_block,Data:1,TileEntityData:{auto:1b,Command:"gamerule mobGriefing false"},Time:1,DropItem:0,Passengers:[{id:"falling_block",Block:repeating_command_block,Data:1,TileEntityData:{auto:1b,Command:"gamerule doWeatherCycle false"},Time:1,DropItem:0,Passengers:[{id:"falling_block",Block:repeating_command_block,Data:1,TileEntityData:{auto:1b,Command:"gamerule keepInventory true"},Time:1,DropItem:0,Passengers:[{id:"falling_block",Block:repeating_command_block,Data:1,TileEntityData:{auto:1b,Command:"gamerule doDaylightCycle false"},Time:1,DropItem:0,Passengers:[{id:"falling_block",Block:repeating_command_block,Data:1,TileEntityData:{auto:1b,Command:"gamerule doMobSpawning false"},Time:1,DropItem:0,Passengers:[{id:"falling_block",Block:repeating_command_block,Data:1,TileEntityData:{auto:1b,Command:"gamerule commandBlockOutput false"},Time:1,DropItem:0}]}]}]}]}]}]}

This command will set multiple gamerules that affect weather, the time cycle, mob griefing, and mob spawning. To pick up the command block that gives you the command, hold Ctrl and press the middle mouse button. After this, set it to a toolbar by pressing C and then a number. Enjoy!