Leopard geckos are insectavores. They need live insects to fulfill their nutritional needs. IF you feed them canned food they probably wont eat it and they will probably lose a lot of weight and become very unhealthy. Unfortunately, when you got into leopard geckos, you got into feeding live feeder, they go hand and hand.
the stuff you feed your feeders so they are fat and plump
Best gutload for crickets and mealworms would be a layer of oats or bran and put in a carrot or potato for vitamins and liquid. crickets also require water offered in the shape of water crystals. They can easily drown in a bowl of water.
Personally i put a coffee cup filled with rocks and water in my cricket enclosure. The rocks make it harder to drown in.
Carrots are great for feeding since they don't get mouldy quickly and rather dry out than go rotting.
It's up to the individual what to feed, but some have found that leos get bored with the same food over and over again.. just something to think about.
There are lots of live feeders you can use if mealies or crickets make you cringe. There are beetles, roaches (though i doubt that is better) and caterpillars/ worms ( Butter Worms, Earth Worms, Silk/Green Horn Worms, and phoenix worms)
I recommend anything but crickets! Those things are nasty. Worms are easily kept and easy to breed and gutload yourself.