In real life Panna Cotta recipes have heavy cream(s), a vanilla and unflavored gelatin. Some recipes use half-and-half instead of cream(s) and some use a combination of the two.
With that in mind, for a basic Panna Cotta recipe I would start with this:
FA Madagascar (Vanilla Classic) 3%
FA Whipped Cream 1.5%
FLV Cream 1%
FA Milk 0.75%
Alternatively, you could go with FA Vanilla Bourbon for a darker more earthy vanilla to make it more tasty and less generic. If you do, go with a lower percent, like 2%, or it will take over the mix.
I think that would give you a decent Panna Cotta base. Then add whatever fruit(s), chocolate, nut, caramel, butterscotch or whatever other flavor(s) you might like over the top.
Panna Cotta Tiramisu would also be tasty. It you like FA Tiramisu go with 0.25% (it's strong). The tiramisu would add some tartness to the Panna Cotta. Same thing with adding a coffee flavor like FA Cappuccino or FA Dark Bean (Coffee Expresso).
Hope that helps!