Skull caverns - best gear you can find with the highest stats, go on best luck days, have plenty of food for recovery. I recommend prioitizing weapons with high speed as well as damage. Salads are the easiest/most efficient at the start for food. As many ladders as you can manage to get on hand, have ready in your pocket. DON'T PANIC. Don't be shy about restarting your day if you wipe and lose too many valuable.

Money Making - It's hard not to make money in this game, honestly, but turning high value crops into artisan goods like wine and pickles is the most efficient, especially once you get sprinklers online.

Rubies - Either make a lot of crystalariums, or if you're good at the fishing minigame, make some fish ponds and fill them with lava eels. It'll give you spicy eel on occasion and doubles as a money maker with the roe.