strobes wiring

hey i was wondering if anyone here could help me figure out how to wire strobes to my reverse lights. i hooked everything up and it backfeeds to the other light. so when i turn the strobes to alternate they both flash at the same time. ive been told i can use a diode. but i dont know what size i need to use. i have an amp meter and digital multimeter if those readings will help. im pretty good with wiring too. me and my dad tried using a relay of some sort and separated the leads to the reverse light. so when the wire leading to the light powered it closed the relay letting the reverse light shine solid. but take it out and the reverse light was completely isolated. everything is hooked up right. but it back feeds off the ground now. i would rather not use another relay for the ground as they are all tied together heading into the tailight housing. so im stuck now.

no its just a cheap strobe kit from autozone. came with LED bulbs that had adhesive on the back. cut those off and used my LED reverse lights. instead. but if i only have one side hooked up they will both blink... kinda defeats the purpose. and i cant justify spending more than like $30 since its not a show car

DId the kit come with a relay?

no it didnt come with the relay. just a box when you power it and turn it on the leds flash. its similar to this kit http:////Pilot-Head-Bumper-Corner-Tail-Light-Strobe-Kit-WI-20_W0QQitemZ330316717414QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item4ce8691d66&_trksid=p4506.c0.m245&_trkparms=65%3A12|39%3A1|72%3A1171

That appears to be a one output strobe kit.  It does not have provisions to operate as a WigWag setup. 

by wig wag do you mean alternate beetween bulbs then yes it does that. you can control speed and how many flashes each pass. and if you want them to alternate

anyone know what kind of diode i could use so it wont backfeed? i dont see how the type of kit would affect that?