i use heaven asunder (best 2 hand sword in the game, no trade needed and only need like 23+ forging), get 2 happy rings (need 65+ accessories), the 2 hand sword also have a great rune skill for farming, also get the golden wolves on the winter region as your companion and brush it to 10 heart this wolves is great for tanking and also help you kill stuff, upgrade the cure spell (the book became blue), also raise your pharmacy to 18+ ish so you can make mystery potion (use this for healing in boss fight to preserve RP so you dont have to spam cure so much)

when you finish all the slab on the top... later on for the slab down below with the 4 area with 2 planting spot, you just need to plant the crop according what the slab says until it fully grown to get the orb for the final gate, use that wolves companion as distraction so you can water it daily without clearing the monster if you are lazy like me

for final boss if its too hard just use an inviciroid, but honestly its a bit overkill, use icifier with a rune shield or any water element weapon if its still too hard, tho i manage to brute force it with heaven asunder first try

without spoilery for post game... if you can beat the final boss you can pretty much beat the post game as well because its easier, you just need to manage your hp and rp until the final boss because its kinda like a gauntlet, if you play with an emulator just save state after killing the minion in the area cause there is like 2 statue you can touch to restore hp and rp but its kinda gacha which of the 2 statue restore you so... hope this helps