Stay nearby to the Worldborder-Center to move it!
This One-Command is multiplayer compatible.
If you don't want 20-100 Massages per second this would help:
/gamerule commandBlockOutput false

Here is the One Command!

summon falling_block ~ ~1 ~ {Block:stone,Time:1,Passengers:[{id:falling_block,Block:redstone_block,Time:1,Passengers:{id:falling_block,Block:activator_rail,Time:1,Passengers:{id:commandblock_minecart,Command:gamerule commandBlockOutput false},{id:commandblock_minecart,Command:/worldborder set 33 10},{id:commandblock_minecart,Command:fill ~3 ~-2 ~ ~7 ~-2 ~1 chain_command_block 5},{id:commandblock_minecart,Command:setblock ~3 ~-2 ~1 chain_command_block 3},{id:commandblock_minecart,Command:fill ~7 ~-2 ~1 ~4 ~-2 ~1 chain_command_block 4},{id:commandblock_minecart,Command:setblock ~7 ~-2 ~ chain_command_block 3},{id:commandblock_minecart,Command:setblock ~3 ~-2 ~ repeating_command_block 5},{id:commandblock_minecart,Command:blockdata ~3 ~-2 ~1 {auto:1,Command:"/summon armor_stand ~ ~1 ~ {CustomName:\\\"Worldborder-Center\\\",CustomNameVisible:1,UUIDLeast:1L,UUIDMost:1L,Tags:\\\"border\\\"],NoGravity:1b,Small:1,Marker:1b,Invisible:1,Invulnerable:1}"}},{id:commandblock_minecart,Command:blockdata ~4 ~-2 ~1 {auto:1,Command:execute @e[tag=border] ~ ~ ~ /particle fireworksSpark ~ ~0.5 ~ 0.1 0.1 0.1 0 5 force @a[r=5]}},{id:commandblock_minecart,Command:blockdata ~5 ~-2 ~1 {auto:1,Command:execute @e[tag=border] ~ ~-2 ~ execute @a[r=2] ~ ~2 ~ tp @e[tag=border] ~ ~-0.05 ~}},{id:commandblock_minecart,Command:blockdata ~6 ~-2 ~1 {auto:1,Command:execute @e[tag=border] ~ ~2 ~ execute @a[r=2] ~ ~-2 ~ tp @e[tag=border] ~ ~0.05 ~}},{id:commandblock_minecart,Command:blockdata ~7 ~-2 ~1 {auto:1,Command:execute @e[tag=border] ~ ~ ~-2 execute @a[r=2] ~ ~ ~2 tp @e[tag=border] ~ ~ ~-0.05}},{id:commandblock_minecart,Command:blockdata ~7 ~-2 ~ {auto:1,Command:execute @e[tag=border] ~ ~ ~2 execute @a[r=2] ~ ~ ~-2 tp @e[tag=border] ~ ~ ~0.05}},{id:commandblock_minecart,Command:blockdata ~6 ~-2 ~ {auto:1,Command:execute @e[tag=border] ~-2 ~ ~ execute @a[r=2] ~2 ~ ~ tp @e[tag=border] ~-0.05 ~ ~}},{id:commandblock_minecart,Command:blockdata ~5 ~-2 ~ {auto:1,Command:execute @e[tag=border] ~2 ~ ~ execute @a[r=2] ~-2 ~ ~ tp @e[tag=border] ~0.05 ~ ~}},{id:commandblock_minecart,Command:blockdata ~4 ~-2 ~ {auto:1,Command:execute @e[tag=border] ~ ~ ~ /setworldspawn}},{id:commandblock_minecart,Command:blockdata ~3 ~-2 ~ {auto:1,Command:execute @e[tag=border] ~ ~ ~ /worldborder center ~ ~ }},{id:commandblock_minecart,Command:setblock ~ ~ ~1 command_block 0 0 {Command:fill ~ ~-3 ~-1 ~ ~ ~ air}},{id:commandblock_minecart,Command:setblock ~ ~-1 ~1 redstone_block},{id:commandblock_minecart,Command:kill @e[type=commandblock_minecart,r=1]}]}]}]}