Well Cheap shot in particular is pretty much useless on Fiddle, it's good only on champs that can perma procc it such as Nautilus. As for Indigenous hunter/ultimate hunter - they're fine but you have to stack them first to be useful - and if you are going Zhonya's into Shureliya's they are probably very good for sure! Biscuit just guarantees you winning lane.
Font of life is actually horrible on Fiddle because of multiple reasons:
1. You can only procc it with your Q
2. It scales off your max hp - Fiddle is not a tanky champ by default - and he doesn't buy that that many hp items anyway
3. The raw stats numbers on it are just not very good, it needs to be buffed.
You can try to check how much value it gives you in your 'Runes' section in your match history and you'll see it's not very effective. You only procc it on one target at a time. And even on Champions like Janna that can procc it on 5 it's just average. Demolish is just way better since you always push with Fiddle and get turret platings - which is free gold

Thanks!