All the runs I've seen have Simon farm 50+ hearts at the very start by going west of Jova to fight the salamander creatures. My biggest problem with this has been timing my whips so that they can't shoot the fireball at me. I've sometimes managed to do it by pure accident but I'm wondering if there is a specific visual/audio cue to becoming more consistent at it?
The best advice I can give you is that Simon's whip animation takes 20 frames, so you can basically whip that fast. There's some rhythm and timing to it, but one of the easiest ways to practice is to launch the game, and then hold right and try to whip in rhythm. If you are frame perfect with it, Simon will literally not move forward at all. If he moves forward then whips, that means you were late. if he moves forward without whipping, it means you were early. Eventually you can try to play a game with yourself on how many whips in a row you can do without Simon moving, then try to break that record. I play on hardware, so my visual cue when I was learning was when I saw the whip fully extended, but everyone's different and with enough practice you'll learn to "feel" the rhythm of it.
With the lizardmen (salamanders), if you're perfect on all four whips, you'll actually be TOO fast and cause the heart to drop too far left and spawn the wolf when you pick it up. Still, that's a better problem to have than not fast enough. You'll eventually get a feel for slowing down on the last whip to let them move right a bit for easy collection.
Additionally, for potentially your own sanity, they are invulnerable for the frame that they shoot the fireball. Early on you will probably be not quite fast enough and get hit with a fireball even though you thought you whipped them. Don't worry, this means you're getting closer/better!
If any of the other players say anything different from me, please take their advise over mine, as they're much more knowledgeable than me. This was just how I learned it. I hope it helps!