The measure of a good Skull Cavern dive is usually measured by your haul of loot, particularly iridium ore and prismatic shards. In isolation, simply getting down to any particular floor means little, other than the achievement of getting there, so the question is how much stuff did you get?
On a related note, with mob drops and treasure floors, there is a huge variety of loot to be had from Skull Cavern, so you want to enter with as many free inventory slots as possible. From your top row alone, assuming that the quality sprinklers came from a treasure floor, you have at least six inventory slots wasted by the following unnecessary items
- Axe
- Scythe
- Hoe
- Watering can
- Fishing rod
- Hardwood
To get the most out of your skull expeditions, you need to commit fully to it, to the exclusion of all other activities, so all of those items should have been left in a chest at the farm.
IMO, you only really need the following slots when you go in
- Weapon
- One single stack of healing food (salads from Gus are good)
- Pickaxe
- Stones/staircases
- Stack of coffee (+1 speed buff)
- Several spicy eel (+1 speed and luck buffs)
- Bombs
- Slingshot loaded with ammo, if you want
This will leave about 28 free spots for loot. You want both speed buffs, because then you can actually outrun the green serpents.