Chris Jordan hit 37 from 26 balls to help Sussex reach 222-9 at Cricket Field Road after being put in by Kent.
Sussex openers Chris Nash and Luke Wright gave the Sharks a good start and they looked comfortable as they crusied to 63-0 from 10 overs.
Wright looked particularly good with some trademark cuts and drives, including a big six into the tennis courts.
But in attempting another six into the tennis courts, Wright skied Adam Ball straight to Darren Stevens for 31.
Very next ball, Luke Wells fell lbw to James Tredwell for a golden duck and the Sharks suddenly looked less comfortable at 63-2.
Rory Hamilton-Brown then joined Nash and the pair put on 25 before Nash (33) flicked Adam Riley to Brendan Nash.
Yardy then joined Hamilton-Brown and the pair kept the total ticking over and they took a liking to Stevens in the 23rd over, hitting 15, including a huge six from Yardy which nearly hit the ice cream van situated next to the tennis courts.
Yardy then hit two fours off a Tredwell over before Hamilton-Brown (40) was run out after some great fielding from Stevens leaving Sussex 143-4 from 26 overs.
Yardy then almost run himself out after a misfield but just made it home as Sussex reached 155-4 from 28 overs. But the former skipper did persih in the next over, clean bowled by Tredwell for 42 from 40 balls.
A poor shot from Gatting saw him caught at mid-off by Tredwell off Riley and the chance of a good total was diminishing fast.
Sussex took their batting powerplay in the 35th over and Chris Jordan welcomed it with a glorious lofted drive for four.
But Ben Brown then lost his middle stump to Ball before Michael Rippon ran needlessly himself out first ball leaving Sussex 181-8 with 5 overs left.
James Anyon then went for a duck in 36th over after bizarrely flicking Ball over his head and being caught by keeper Geraint Jones and it was touch and go whether Sussex would reach 200.
But Chris Jordan and Chris Liddle had other ideas and hit 27 off the last two overs to give the total some respectability.
The Kent spinners Riley (2-34) and Tredwell (2-43) were impressive as they restricted the Sharks in the middle of the innings. Adam Ball took 3-35.