I have a friend who mixes canned pudding with her frosting for the filling. Then she uses regular frosting to frost it.

I run preserves through the blender to cut down the lumps, and put that on top of the bottom layer. Then I put frosting on top of that. Then put the layers together and frost as usual.

Sometimes I mix drained fruit (pineapple, cherries, etc.) in with some of the frosting to make a filling.

Once I piped a ring of frosting around the top edge of the bottom layer (use a larger tube). The a ring of jam next to it. Alternate... it looks very pretty when you cut the cake.

Have fun.