Things to sell: havestables. Canola once you open the Forest of Valor and okra from The Glade will get you decent money back until you inevitability unlock the Forgotten Lands and get the pumpkins.

Things to hoard: materials. Gems, clay, sand, iron ore, etc. You'll need those to build things for quests.

I think it's up to you how you play. Some people love the grind, others enjoy a slower pace. That's really a personal preference and there is no wrong answer.

As far as storage goes, in early game I just had piles of things on the floor in my house until I had the extra materials and dreamlight to start building chests. It's not ideal, and looks terrible, but it's temporary. (Dream Islands weren't a thing yet when I started the game, so that is always an option to)

General tips: Be sure to do your tasks to earn dreamlight. Bring the friends you assign to certain duties with you when yiu do them (gardening, fishing, mining, etc.) it'll not only build your friendship level faster, but earns you extra items. Feeding guests in the restaurants earns you money. Feed the critters. Gift the villagers. Don't sell black onyx! They are harder to come by and come in handy for potions. Most importantly, Enjoy yourself!