CRJ900 pilot reported wing tip made contact with a fuel truck during taxi into the gate.

Narrative

Upon taxiing into gate XX at ZZZ; the aircraft's left wingtip made contact with a fuel truck. Gate XX requires multiple marshalers due to the angle at which the aircraft must enter prior to turning to park. Before entering the immediate gate area; the Captain and I concurred that the vehicles on the left side were in a safe area; as marked on the pavement. The marshalers appeared to be training; as the first to guide us in had someone standing immediately behind them directing them. Marshaler #2; who directs us to slow and stop the aircraft was on their own. We taxied into the gate using standard procedures and a standard safe speed. Marshaler #2 raised both wands signaling us to slow; and the Captain began to further slow the aircraft approaching a stop. Marshaler #2 gave a nonstandard signal that can only be described as them with both wands in the air pointing in the direction of the nose of the aircraft. Another person (supervisor; trainer?) came running up to them from the side holding their arms in an X and told marshaler #2 to signal the 'stop' X to us. We stopped the aircraft at this signal and performed a normal shutdown procedure. Upon 'chocks in' signal and main cabin door opening; our forward Flight Attendant (FA) notified us that one of the ramp personnel was moving right under the door of the aircraft during door opening and she felt it was unsafe. Captain talked with a supervisor out on the ramp about their training and not letting personnel move around the aircraft like that during door opening. At no point did any ramp personnel notify us that our wingtip had made contact with a vehicle during parking. Nothing with the aircraft seemed abnormal to us in the flight deck. I was notified by the Dispatch duty pilot via email approximately 7 hours after the event that this had occurred. In my opinion; the marshaler improperly directed us too far forward in the parking area which caused the wingtip to exit the safety zone of the gate area and strike a fuel truck. There were a lot of ground personnel present in the gate area; and it seems that the ground crew's inexperience / training operations was a factor in this incident. A change in ramp personnel training procedures that wouldn't leave a sole inexperienced agent directing the aircraft to its final stopping point.