Maybe you're under-leveled? Enemies drop enough of them, food, drinks, plus there are couple points where it restores hp/en, adds potions, food, drinks.
10 cheapest and 8 mid-grade potions were enough for me then I was testing this with lvl 8 party. You have an option to skip a lot of encounters if it's too hard for you choosing different routes.
Most of the drops are energy items which are nowhere near as important as health items.
I am level 7 (becoming 8 during the run). 5 100% and 8 75% and a few of the weaker ones got me to the estate (plus what i found along the way). After learning how to battle efficiently after the third try.
Ofc you as the dev will have an easy time doing it optimally. I don't think that applies to the rest of us. Atleast give us an opportunity to refill pots at the estate. As it is, it is ridiculous tbh.
I would most prefer if Retreating was an actual option between battles, so you could see "ok, I will have to go back now and try again" instead of "ok, i will have to reload and do it all over again without my new skills etc". It just
feels so bad. And if you make it to the estate, make it an option to start from there. That would in my eyes be better game design.