In order to do this method, you will need to be at "endgame", and have 5 skill points allocated to gaining extra EXP. It's of course possible without these 5 points as well, but you will have a much lower EXP per hour that way.
The farming method to get 270k EXP and 100k+ Gols dailyDirectly after you wake up, head to the dee-dee stop and go to The Deepest Ruins (Somber Marsh) floor 97. When you are in, buy 1x Lucky Bean for 1 Challenger Coin, since this item doubles your materials. Now head towards the Piggy-bot 002 and attack it until it dies, preferable with the Rogue Sword (or else it takes longer).
Each Piggy-bot 002 gives you 13,500 EXP. Now go to the exit and chose Floor 97 once again. Do not go trough the door after you kill the Piggy-bot!
Anyway, re-enter floor 97 and kill the Piggy-bot 002 once more for another 13,500 EXP. Now do this for the next 10 minutes and you will on average get just over 100k Gols and 270,000 EXP per in-game day. Each run "costs" 1 hour of in-game time, but you can of course just go to bed and begin again. But remember to buy a new Lucky Bean!
The exact amount of Gols you get from selling all the items will vary since the drop rates are different each day, but it will average out to just over 100k in the long-run.